* [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
@ 2020-08-27 15:36 ` Dr. David Alan Gilbert (git)
0 siblings, 0 replies; 41+ messages in thread
From: Dr. David Alan Gilbert (git) @ 2020-08-27 15:36 UTC (permalink / raw)
To: qemu-devel, vgoyal, stefanha, virtio-fs
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Add an option to define mappings of xattr names so that
the client and server filesystems see different views.
This can be used to have different SELinux mappings as
seen by the guest, to run the virtiofsd with less privileges
(e.g. in a case where it can't set trusted/system/security
xattrs but you want the guest to be able to), or to isolate
multiple users of the same name; e.g. trusted attributes
used by stacking overlayfs.
A mapping engine is used wit 3 simple rules; the rules can
be combined to allow most useful mapping scenarios.
The ruleset is defined by -o xattrmap='rules...'.
This patch doesn't use the rule maps yet.
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
docs/tools/virtiofsd.rst | 55 ++++++++++++
tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
2 files changed, 203 insertions(+)
diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
index 824e713491..2efa16d3c5 100644
--- a/docs/tools/virtiofsd.rst
+++ b/docs/tools/virtiofsd.rst
@@ -107,6 +107,60 @@ Options
performance. ``auto`` acts similar to NFS with a 1 second metadata cache
timeout. ``always`` sets a long cache lifetime at the expense of coherency.
+xattr-mapping
+-------------
+
+By default the name of xattr's used by the client are passed through to the server
+file system. This can be a problem where either those xattr names are used
+by something on the server (e.g. selinux client/server confusion) or if the
+virtiofsd is running in a container with restricted priviliges where it cannot
+access some attributes.
+
+A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
+string consists of a series of rules.
+
+The first matching rule terminates the mapping.
+
+Each rule consists of a number of fields separated with a separator that is the
+first non-white space character in the rule. This separator must then be used
+for the whole rule.
+White space may be added before and after each rule.
+Using ':' as the separator a rule is of the form:
+
+``:scope:type:key:prepend:``
+
+**scope** is:
+
+- 'client' - match 'key' against a xattr name from the client for
+ setxattr/getxattr/removexattr
+- 'server' - match 'prepend' against a xattr name from the server
+ for listxattr
+- 'all' - can be used to match both cases.
+
+**type** is one of:
+
+- 'prefix' - If 'key' matches the client then the 'prepend'
+ is added before the name is passed to the server.
+ For a server case, the prepend is tested and stripped
+ if matching.
+
+- 'ok' - The attribute name is OK and passed through to
+ the server unchanged.
+
+- 'bad' - If a client tries to use this name it's
+ denied using EPERM; when the server passes an attribute
+ name matching it's hidden.
+
+**key** is a string tested as a prefix on an attribute name originating
+on the client. It maybe empty in which case a 'client' rule
+will always match on client names.
+
+**prepend** is a string tested as a prefix on an attribute name originiating
+on the server, and used as a new prefix. It maybe empty
+in which case a 'server' rule will always match on all names from
+the server.
+
+
Examples
--------
@@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
-numa node,memdev=mem \
...
guest# mount -t virtiofs myfs /mnt
+
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 083d17a960..00e96a10cd 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -64,6 +64,7 @@
#include <syslog.h>
#include <unistd.h>
+#include "qemu/cutils.h"
#include "passthrough_helpers.h"
#include "passthrough_seccomp.h"
@@ -144,6 +145,7 @@ struct lo_data {
int flock;
int posix_lock;
int xattr;
+ char *xattrmap;
char *source;
char *modcaps;
double timeout;
@@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
{ "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
{ "xattr", offsetof(struct lo_data, xattr), 1 },
{ "no_xattr", offsetof(struct lo_data, xattr), 0 },
+ { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
{ "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
{ "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
{ "timeout=", offsetof(struct lo_data, timeout_set), 1 },
@@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
fuse_reply_err(req, res == -1 ? errno : 0);
}
+typedef struct xattr_map_entry {
+ const char *key;
+ const char *prepend;
+ unsigned int flags;
+} XattrMapEntry;
+
+/*
+ * Exit; process attribute unmodified if matched.
+ * An empty key applies to all.
+ */
+#define XATTR_MAP_FLAG_END_OK (1 << 0)
+/*
+ * The attribute is unwanted;
+ * EPERM on write hidden on read.
+ */
+#define XATTR_MAP_FLAG_END_BAD (1 << 1)
+/*
+ * For attr that start with 'key' prepend 'prepend'
+ * 'key' maybe empty to prepend for all attrs
+ * key is defined from set/remove point of view.
+ * Automatically reversed on read
+ */
+#define XATTR_MAP_FLAG_PREFIX (1 << 2)
+/* Apply rule to get/set/remove */
+#define XATTR_MAP_FLAG_CLIENT (1 << 16)
+/* Apply rule to list */
+#define XATTR_MAP_FLAG_SERVER (1 << 17)
+/* Apply rule to all */
+#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
+
+static XattrMapEntry *xattr_map_list;
+
+static XattrMapEntry *parse_xattrmap(const char *map)
+{
+ XattrMapEntry *res = NULL;
+ size_t nentries = 0;
+ const char *tmp;
+
+ while (*map) {
+ char sep;
+
+ if (isspace(*map)) {
+ map++;
+ continue;
+ }
+ /* The separator is the first non-space of the rule */
+ sep = *map++;
+ if (!sep) {
+ break;
+ }
+
+ /* Allocate some space for the rule */
+ res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
+ res[nentries - 1].flags = 0;
+
+ if (strstart(map, "client", &map)) {
+ res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
+ } else if (strstart(map, "server", &map)) {
+ res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
+ } else if (strstart(map, "all", &map)) {
+ res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
+ } else {
+ fuse_log(FUSE_LOG_ERR,
+ "%s: Unexpected scope;"
+ " Expecting 'client', 'server', or 'all', in rule %zu\n",
+ __func__, nentries);
+ exit(1);
+ }
+
+
+ if (*map != sep) {
+ fuse_log(FUSE_LOG_ERR,
+ "%s: Expecting '%c' found '%c'"
+ " after scope in rule %zu\n",
+ __func__, sep, *map, nentries + 1);
+ exit(1);
+ }
+ /* Skip the separator, now at the start of the 'type' */
+ map++;
+
+ /* Start of 'type' */
+ if (strstart(map, "prefix", &map)) {
+ res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
+ } else if (strstart(map, "ok", &map)) {
+ res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
+ } else if (strstart(map, "bad", &map)) {
+ res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
+ } else {
+ fuse_log(FUSE_LOG_ERR,
+ "%s: Unexpected type;"
+ "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
+ __func__, nentries);
+ exit(1);
+ }
+
+ if (*map++ != sep) {
+ fuse_log(FUSE_LOG_ERR,
+ "%s: Missing '%c' at end of type field of rule %zu\n",
+ __func__, sep, nentries);
+ exit(1);
+ }
+
+ /* At start of 'key' field */
+ tmp = strchr(map, sep);
+ if (!tmp) {
+ fuse_log(FUSE_LOG_ERR,
+ "%s: Missing '%c' at end of key field of rule %zu",
+ __func__, sep, nentries);
+ exit(1);
+ }
+ res[nentries - 1].key = g_strndup(map, tmp - map);
+ map = tmp + 1;
+
+ /* At start of 'prepend' field */
+ tmp = strchr(map, sep);
+ if (!tmp) {
+ fuse_log(FUSE_LOG_ERR,
+ "%s: Missing '%c' at end of prepend field of rule %zu",
+ __func__, sep, nentries);
+ exit(1);
+ }
+ res[nentries - 1].prepend = g_strndup(map, tmp - map);
+ map = tmp + 1;
+ /* End of rule - go around again for another rule */
+ }
+
+ if (!nentries) {
+ fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
+ exit(1);
+ }
+
+ /* Add a terminator to error in cases the user hasn't specified */
+ res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
+ res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
+ res[nentries - 1].key = g_strdup("");
+ res[nentries - 1].prepend = g_strdup("");
+
+ return res;
+}
+
static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
size_t size)
{
@@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
} else {
lo.source = strdup("/");
}
+
+ if (lo.xattrmap) {
+ xattr_map_list = parse_xattrmap(lo.xattrmap);
+ }
+
if (!lo.timeout_set) {
switch (lo.cache) {
case CACHE_NONE:
--
2.26.2
^ permalink raw reply related [flat|nested] 41+ messages in thread* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
2020-08-27 15:36 ` Dr. David Alan Gilbert (git)
@ 2020-09-09 11:20 ` Ján Tomko
-1 siblings, 0 replies; 41+ messages in thread
From: Ján Tomko @ 2020-09-09 11:20 UTC (permalink / raw)
To: Dr. David Alan Gilbert (git); +Cc: virtio-fs, qemu-devel, vgoyal
[-- Attachment #1: Type: text/plain, Size: 3671 bytes --]
On a Thursday in 2020, Dr. David Alan Gilbert (git) wrote:
>From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
>Add an option to define mappings of xattr names so that
>the client and server filesystems see different views.
>This can be used to have different SELinux mappings as
>seen by the guest, to run the virtiofsd with less privileges
>(e.g. in a case where it can't set trusted/system/security
>xattrs but you want the guest to be able to), or to isolate
>multiple users of the same name; e.g. trusted attributes
>used by stacking overlayfs.
>
>A mapping engine is used wit 3 simple rules; the rules can
>be combined to allow most useful mapping scenarios.
>The ruleset is defined by -o xattrmap='rules...'.
>
>This patch doesn't use the rule maps yet.
>
>Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>---
> docs/tools/virtiofsd.rst | 55 ++++++++++++
> tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> 2 files changed, 203 insertions(+)
>
>diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
>index 824e713491..2efa16d3c5 100644
>--- a/docs/tools/virtiofsd.rst
>+++ b/docs/tools/virtiofsd.rst
>@@ -107,6 +107,60 @@ Options
> performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> timeout. ``always`` sets a long cache lifetime at the expense of coherency.
>
>+xattr-mapping
>+-------------
>+
>+By default the name of xattr's used by the client are passed through to the server
>+file system. This can be a problem where either those xattr names are used
>+by something on the server (e.g. selinux client/server confusion) or if the
>+virtiofsd is running in a container with restricted priviliges where it cannot
privileges
>+access some attributes.
>+
>+A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
>+string consists of a series of rules.
>+
>+The first matching rule terminates the mapping.
>+
>+Each rule consists of a number of fields separated with a separator that is the
>+first non-white space character in the rule. This separator must then be used
>+for the whole rule.
>+White space may be added before and after each rule.
>+Using ':' as the separator a rule is of the form:
>+
>+``:scope:type:key:prepend:``
>+
>+**scope** is:
>+
>+- 'client' - match 'key' against a xattr name from the client for
>+ setxattr/getxattr/removexattr
>+- 'server' - match 'prepend' against a xattr name from the server
>+ for listxattr
>+- 'all' - can be used to match both cases.
>+
>+**type** is one of:
>+
>+- 'prefix' - If 'key' matches the client then the 'prepend'
>+ is added before the name is passed to the server.
>+ For a server case, the prepend is tested and stripped
>+ if matching.
>+
>+- 'ok' - The attribute name is OK and passed through to
>+ the server unchanged.
>+
>+- 'bad' - If a client tries to use this name it's
>+ denied using EPERM; when the server passes an attribute
>+ name matching it's hidden.
>+
>+**key** is a string tested as a prefix on an attribute name originating
>+on the client. It maybe empty in which case a 'client' rule
>+will always match on client names.
>+
>+**prepend** is a string tested as a prefix on an attribute name originiating
originating
>+on the server, and used as a new prefix. It maybe empty
may be
>+in which case a 'server' rule will always match on all names from
>+the server.
>+
>+
> Examples
> --------
>
>@@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> -numa node,memdev=mem \
> ...
> guest# mount -t virtiofs myfs /mnt
>+
git complains about trailing whitespace at EOF
Jano
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
^ permalink raw reply [flat|nested] 41+ messages in thread
* Re: [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
@ 2020-09-09 11:20 ` Ján Tomko
0 siblings, 0 replies; 41+ messages in thread
From: Ján Tomko @ 2020-09-09 11:20 UTC (permalink / raw)
To: Dr. David Alan Gilbert (git); +Cc: virtio-fs, stefanha, qemu-devel, vgoyal
[-- Attachment #1: Type: text/plain, Size: 3671 bytes --]
On a Thursday in 2020, Dr. David Alan Gilbert (git) wrote:
>From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
>Add an option to define mappings of xattr names so that
>the client and server filesystems see different views.
>This can be used to have different SELinux mappings as
>seen by the guest, to run the virtiofsd with less privileges
>(e.g. in a case where it can't set trusted/system/security
>xattrs but you want the guest to be able to), or to isolate
>multiple users of the same name; e.g. trusted attributes
>used by stacking overlayfs.
>
>A mapping engine is used wit 3 simple rules; the rules can
>be combined to allow most useful mapping scenarios.
>The ruleset is defined by -o xattrmap='rules...'.
>
>This patch doesn't use the rule maps yet.
>
>Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>---
> docs/tools/virtiofsd.rst | 55 ++++++++++++
> tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> 2 files changed, 203 insertions(+)
>
>diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
>index 824e713491..2efa16d3c5 100644
>--- a/docs/tools/virtiofsd.rst
>+++ b/docs/tools/virtiofsd.rst
>@@ -107,6 +107,60 @@ Options
> performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> timeout. ``always`` sets a long cache lifetime at the expense of coherency.
>
>+xattr-mapping
>+-------------
>+
>+By default the name of xattr's used by the client are passed through to the server
>+file system. This can be a problem where either those xattr names are used
>+by something on the server (e.g. selinux client/server confusion) or if the
>+virtiofsd is running in a container with restricted priviliges where it cannot
privileges
>+access some attributes.
>+
>+A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
>+string consists of a series of rules.
>+
>+The first matching rule terminates the mapping.
>+
>+Each rule consists of a number of fields separated with a separator that is the
>+first non-white space character in the rule. This separator must then be used
>+for the whole rule.
>+White space may be added before and after each rule.
>+Using ':' as the separator a rule is of the form:
>+
>+``:scope:type:key:prepend:``
>+
>+**scope** is:
>+
>+- 'client' - match 'key' against a xattr name from the client for
>+ setxattr/getxattr/removexattr
>+- 'server' - match 'prepend' against a xattr name from the server
>+ for listxattr
>+- 'all' - can be used to match both cases.
>+
>+**type** is one of:
>+
>+- 'prefix' - If 'key' matches the client then the 'prepend'
>+ is added before the name is passed to the server.
>+ For a server case, the prepend is tested and stripped
>+ if matching.
>+
>+- 'ok' - The attribute name is OK and passed through to
>+ the server unchanged.
>+
>+- 'bad' - If a client tries to use this name it's
>+ denied using EPERM; when the server passes an attribute
>+ name matching it's hidden.
>+
>+**key** is a string tested as a prefix on an attribute name originating
>+on the client. It maybe empty in which case a 'client' rule
>+will always match on client names.
>+
>+**prepend** is a string tested as a prefix on an attribute name originiating
originating
>+on the server, and used as a new prefix. It maybe empty
may be
>+in which case a 'server' rule will always match on all names from
>+the server.
>+
>+
> Examples
> --------
>
>@@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> -numa node,memdev=mem \
> ...
> guest# mount -t virtiofs myfs /mnt
>+
git complains about trailing whitespace at EOF
Jano
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
^ permalink raw reply [flat|nested] 41+ messages in thread
* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
2020-09-09 11:20 ` Ján Tomko
@ 2020-09-10 18:38 ` Dr. David Alan Gilbert
-1 siblings, 0 replies; 41+ messages in thread
From: Dr. David Alan Gilbert @ 2020-09-10 18:38 UTC (permalink / raw)
To: Ján Tomko; +Cc: virtio-fs, qemu-devel, vgoyal
* Ján Tomko (jtomko@redhat.com) wrote:
> On a Thursday in 2020, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Add an option to define mappings of xattr names so that
> > the client and server filesystems see different views.
> > This can be used to have different SELinux mappings as
> > seen by the guest, to run the virtiofsd with less privileges
> > (e.g. in a case where it can't set trusted/system/security
> > xattrs but you want the guest to be able to), or to isolate
> > multiple users of the same name; e.g. trusted attributes
> > used by stacking overlayfs.
> >
> > A mapping engine is used wit 3 simple rules; the rules can
> > be combined to allow most useful mapping scenarios.
> > The ruleset is defined by -o xattrmap='rules...'.
> >
> > This patch doesn't use the rule maps yet.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> > docs/tools/virtiofsd.rst | 55 ++++++++++++
> > tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> > 2 files changed, 203 insertions(+)
> >
> > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> > index 824e713491..2efa16d3c5 100644
> > --- a/docs/tools/virtiofsd.rst
> > +++ b/docs/tools/virtiofsd.rst
> > @@ -107,6 +107,60 @@ Options
> > performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> > timeout. ``always`` sets a long cache lifetime at the expense of coherency.
> >
> > +xattr-mapping
> > +-------------
> > +
> > +By default the name of xattr's used by the client are passed through to the server
> > +file system. This can be a problem where either those xattr names are used
> > +by something on the server (e.g. selinux client/server confusion) or if the
> > +virtiofsd is running in a container with restricted priviliges where it cannot
>
> privileges
Fixed.
> > +access some attributes.
> > +
> > +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> > +string consists of a series of rules.
> > +
> > +The first matching rule terminates the mapping.
> > +
> > +Each rule consists of a number of fields separated with a separator that is the
> > +first non-white space character in the rule. This separator must then be used
> > +for the whole rule.
> > +White space may be added before and after each rule.
> > +Using ':' as the separator a rule is of the form:
> > +
> > +``:scope:type:key:prepend:``
> > +
> > +**scope** is:
> > +
> > +- 'client' - match 'key' against a xattr name from the client for
> > + setxattr/getxattr/removexattr
> > +- 'server' - match 'prepend' against a xattr name from the server
> > + for listxattr
> > +- 'all' - can be used to match both cases.
> > +
> > +**type** is one of:
> > +
> > +- 'prefix' - If 'key' matches the client then the 'prepend'
> > + is added before the name is passed to the server.
> > + For a server case, the prepend is tested and stripped
> > + if matching.
> > +
> > +- 'ok' - The attribute name is OK and passed through to
> > + the server unchanged.
> > +
> > +- 'bad' - If a client tries to use this name it's
> > + denied using EPERM; when the server passes an attribute
> > + name matching it's hidden.
> > +
> > +**key** is a string tested as a prefix on an attribute name originating
> > +on the client. It maybe empty in which case a 'client' rule
> > +will always match on client names.
> > +
> > +**prepend** is a string tested as a prefix on an attribute name originiating
>
> originating
Done.
> > +on the server, and used as a new prefix. It maybe empty
>
> may be
OK
> > +in which case a 'server' rule will always match on all names from
> > +the server.
> > +
> > +
> > Examples
> > --------
> >
> > @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> > -numa node,memdev=mem \
> > ...
> > guest# mount -t virtiofs myfs /mnt
> > +
>
> git complains about trailing whitespace at EOF
Eaten.
Dave
> Jano
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 41+ messages in thread
* Re: [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
@ 2020-09-10 18:38 ` Dr. David Alan Gilbert
0 siblings, 0 replies; 41+ messages in thread
From: Dr. David Alan Gilbert @ 2020-09-10 18:38 UTC (permalink / raw)
To: Ján Tomko; +Cc: virtio-fs, stefanha, qemu-devel, vgoyal
* Ján Tomko (jtomko@redhat.com) wrote:
> On a Thursday in 2020, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Add an option to define mappings of xattr names so that
> > the client and server filesystems see different views.
> > This can be used to have different SELinux mappings as
> > seen by the guest, to run the virtiofsd with less privileges
> > (e.g. in a case where it can't set trusted/system/security
> > xattrs but you want the guest to be able to), or to isolate
> > multiple users of the same name; e.g. trusted attributes
> > used by stacking overlayfs.
> >
> > A mapping engine is used wit 3 simple rules; the rules can
> > be combined to allow most useful mapping scenarios.
> > The ruleset is defined by -o xattrmap='rules...'.
> >
> > This patch doesn't use the rule maps yet.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> > docs/tools/virtiofsd.rst | 55 ++++++++++++
> > tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> > 2 files changed, 203 insertions(+)
> >
> > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> > index 824e713491..2efa16d3c5 100644
> > --- a/docs/tools/virtiofsd.rst
> > +++ b/docs/tools/virtiofsd.rst
> > @@ -107,6 +107,60 @@ Options
> > performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> > timeout. ``always`` sets a long cache lifetime at the expense of coherency.
> >
> > +xattr-mapping
> > +-------------
> > +
> > +By default the name of xattr's used by the client are passed through to the server
> > +file system. This can be a problem where either those xattr names are used
> > +by something on the server (e.g. selinux client/server confusion) or if the
> > +virtiofsd is running in a container with restricted priviliges where it cannot
>
> privileges
Fixed.
> > +access some attributes.
> > +
> > +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> > +string consists of a series of rules.
> > +
> > +The first matching rule terminates the mapping.
> > +
> > +Each rule consists of a number of fields separated with a separator that is the
> > +first non-white space character in the rule. This separator must then be used
> > +for the whole rule.
> > +White space may be added before and after each rule.
> > +Using ':' as the separator a rule is of the form:
> > +
> > +``:scope:type:key:prepend:``
> > +
> > +**scope** is:
> > +
> > +- 'client' - match 'key' against a xattr name from the client for
> > + setxattr/getxattr/removexattr
> > +- 'server' - match 'prepend' against a xattr name from the server
> > + for listxattr
> > +- 'all' - can be used to match both cases.
> > +
> > +**type** is one of:
> > +
> > +- 'prefix' - If 'key' matches the client then the 'prepend'
> > + is added before the name is passed to the server.
> > + For a server case, the prepend is tested and stripped
> > + if matching.
> > +
> > +- 'ok' - The attribute name is OK and passed through to
> > + the server unchanged.
> > +
> > +- 'bad' - If a client tries to use this name it's
> > + denied using EPERM; when the server passes an attribute
> > + name matching it's hidden.
> > +
> > +**key** is a string tested as a prefix on an attribute name originating
> > +on the client. It maybe empty in which case a 'client' rule
> > +will always match on client names.
> > +
> > +**prepend** is a string tested as a prefix on an attribute name originiating
>
> originating
Done.
> > +on the server, and used as a new prefix. It maybe empty
>
> may be
OK
> > +in which case a 'server' rule will always match on all names from
> > +the server.
> > +
> > +
> > Examples
> > --------
> >
> > @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> > -numa node,memdev=mem \
> > ...
> > guest# mount -t virtiofs myfs /mnt
> > +
>
> git complains about trailing whitespace at EOF
Eaten.
Dave
> Jano
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 41+ messages in thread
* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
2020-08-27 15:36 ` Dr. David Alan Gilbert (git)
@ 2020-09-11 21:13 ` Vivek Goyal
-1 siblings, 0 replies; 41+ messages in thread
From: Vivek Goyal @ 2020-09-11 21:13 UTC (permalink / raw)
To: Dr. David Alan Gilbert (git); +Cc: virtio-fs, qemu-devel
On Thu, Aug 27, 2020 at 04:36:54PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> Add an option to define mappings of xattr names so that
> the client and server filesystems see different views.
> This can be used to have different SELinux mappings as
> seen by the guest, to run the virtiofsd with less privileges
> (e.g. in a case where it can't set trusted/system/security
> xattrs but you want the guest to be able to), or to isolate
> multiple users of the same name; e.g. trusted attributes
> used by stacking overlayfs.
>
> A mapping engine is used wit 3 simple rules; the rules can
> be combined to allow most useful mapping scenarios.
> The ruleset is defined by -o xattrmap='rules...'.
>
> This patch doesn't use the rule maps yet.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> docs/tools/virtiofsd.rst | 55 ++++++++++++
> tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> 2 files changed, 203 insertions(+)
>
> diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> index 824e713491..2efa16d3c5 100644
> --- a/docs/tools/virtiofsd.rst
> +++ b/docs/tools/virtiofsd.rst
> @@ -107,6 +107,60 @@ Options
> performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> timeout. ``always`` sets a long cache lifetime at the expense of coherency.
>
> +xattr-mapping
> +-------------
> +
> +By default the name of xattr's used by the client are passed through to the server
> +file system. This can be a problem where either those xattr names are used
> +by something on the server (e.g. selinux client/server confusion) or if the
> +virtiofsd is running in a container with restricted priviliges where it cannot
> +access some attributes.
> +
> +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> +string consists of a series of rules.
> +
> +The first matching rule terminates the mapping.
> +
> +Each rule consists of a number of fields separated with a separator that is the
> +first non-white space character in the rule. This separator must then be used
> +for the whole rule.
> +White space may be added before and after each rule.
> +Using ':' as the separator a rule is of the form:
> +
> +``:scope:type:key:prepend:``
Hi David,
This seems very genric and which makes it harder to understand and
harder to write rules. I am wondering do we really need this degree
of flexibility. Is it worth, dropping some of the requirements
and simplify the syntax.
- I am wonderig why do we need to allow choice of separator.
- Wondering why do we need to allow separate rules for client/server.
Once we start remapping something, is it not good enough that
mapping be bidirectonal.
- Not sure why separate notion of "bad". To me once we decide to
remap something, should automatically block unprefixed version.
IOW, what functionality we will lose if we just say
-o remap_xattr="trusted.".
This implies following.
A. If client is sending any xattr prefixed with "trusted.", prefix it
with "user.virtiofs".
B. Server filters out anything starting with "trusted."
C. If server sees "user.virtiofs.trusted." it strips "user.virtiofs".
For remapping security.selinux, user could specify.
-o remap_xattr="security.selinux."
For nested configuration. virtiofsd at L1 will specify.
-o remap_xattr="security.selinux.".
And virtiofsd at L0 can specify.
-o remap_xattr="user.virtiofs.security.selinux."
I doubt we need to care about being able to remap xattrs of
other filesystems like virtio-9p.
I also have some questions about how this will be used.
Overlay
-------
- So for non nested guests, we can have two instances of overlay. Lets
call these ovl0 and ovl1. (ovl0 being on host, and ovl1 being inside
guest). Fs hierarcy might look as follows.
ext4-->ovl0-->virtiofsd0-->ovl1
This case does not work by default even if virtiofsd has CAP_SYS_ADMIN
by default as overlay does not allow nesting. So when ovl1 tries to
set trusted.overlay, ovl0 will deny it.
We could simple pass extra directory from host which does not go through
overlay on host and use that as upper inside guest.
ext4-->ovl0-->virtiofsd0-->ovl1
ext4-->ovl0/upper-->virtiofsd0-->ovl1
(/upper used as upper directory of ovl1)
I guess remapping "trusted.overlay" will allow us not to have a separate
ovl0/upper. And following itself will work. Have you tested it? Does
this work. Basically we are creating nested overlay configuration with
virtiofs in between. Is "trusted.overlay" only conflict. I wonder
there might be others. Just that "trusted.overlay" is first failure
we noticed.
Nested Overlay
--------------
- For now I will assume that we are using separate upper dir.
ext4-->ovl0-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2
ext4-->ovl0/upper1-->virtiofsd0-->ovl1(uses upper1 as upperdir)
ext4-->ovl0/upper2-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2 (users upper2
as upper dir)
Basically create two directories upper1 and upper2 on regular filesystem
say ext4/xfs. Bind mount them on ovl0/upper1 and ovl0/upper2 respectively.
And now ovl1 uses ovl0/upper1 as upperdir and ovl2 uses ovl0/upper2 as
upperdir. This should make sure ovl0, ovl1 and ovl2 are not nested from
sharing upper perspective.
Now virtiofsd1 will run with '-o remap_xattr="trusted.overlay"' and
virtiofsd0 will run with '-o remap_xattr="user.virtiofs.trusted.overlay"'
Just trying to wrap my head around how our use cases will use this new
remapping xattr thing.
Thanks
Vivek
> +
> +**scope** is:
> +
> +- 'client' - match 'key' against a xattr name from the client for
> + setxattr/getxattr/removexattr
> +- 'server' - match 'prepend' against a xattr name from the server
> + for listxattr
> +- 'all' - can be used to match both cases.
> +
> +**type** is one of:
> +
> +- 'prefix' - If 'key' matches the client then the 'prepend'
> + is added before the name is passed to the server.
> + For a server case, the prepend is tested and stripped
> + if matching.
> +
> +- 'ok' - The attribute name is OK and passed through to
> + the server unchanged.
> +
> +- 'bad' - If a client tries to use this name it's
> + denied using EPERM; when the server passes an attribute
> + name matching it's hidden.
> +
> +**key** is a string tested as a prefix on an attribute name originating
> +on the client. It maybe empty in which case a 'client' rule
> +will always match on client names.
> +
> +**prepend** is a string tested as a prefix on an attribute name originiating
> +on the server, and used as a new prefix. It maybe empty
> +in which case a 'server' rule will always match on all names from
> +the server.
> +
> +
> Examples
> --------
>
> @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> -numa node,memdev=mem \
> ...
> guest# mount -t virtiofs myfs /mnt
> +
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 083d17a960..00e96a10cd 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -64,6 +64,7 @@
> #include <syslog.h>
> #include <unistd.h>
>
> +#include "qemu/cutils.h"
> #include "passthrough_helpers.h"
> #include "passthrough_seccomp.h"
>
> @@ -144,6 +145,7 @@ struct lo_data {
> int flock;
> int posix_lock;
> int xattr;
> + char *xattrmap;
> char *source;
> char *modcaps;
> double timeout;
> @@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
> { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> { "xattr", offsetof(struct lo_data, xattr), 1 },
> { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> + { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
> { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
> { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
> @@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> fuse_reply_err(req, res == -1 ? errno : 0);
> }
>
> +typedef struct xattr_map_entry {
> + const char *key;
> + const char *prepend;
> + unsigned int flags;
> +} XattrMapEntry;
> +
> +/*
> + * Exit; process attribute unmodified if matched.
> + * An empty key applies to all.
> + */
> +#define XATTR_MAP_FLAG_END_OK (1 << 0)
> +/*
> + * The attribute is unwanted;
> + * EPERM on write hidden on read.
> + */
> +#define XATTR_MAP_FLAG_END_BAD (1 << 1)
> +/*
> + * For attr that start with 'key' prepend 'prepend'
> + * 'key' maybe empty to prepend for all attrs
> + * key is defined from set/remove point of view.
> + * Automatically reversed on read
> + */
> +#define XATTR_MAP_FLAG_PREFIX (1 << 2)
> +/* Apply rule to get/set/remove */
> +#define XATTR_MAP_FLAG_CLIENT (1 << 16)
> +/* Apply rule to list */
> +#define XATTR_MAP_FLAG_SERVER (1 << 17)
> +/* Apply rule to all */
> +#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
> +
> +static XattrMapEntry *xattr_map_list;
> +
> +static XattrMapEntry *parse_xattrmap(const char *map)
> +{
> + XattrMapEntry *res = NULL;
> + size_t nentries = 0;
> + const char *tmp;
> +
> + while (*map) {
> + char sep;
> +
> + if (isspace(*map)) {
> + map++;
> + continue;
> + }
> + /* The separator is the first non-space of the rule */
> + sep = *map++;
> + if (!sep) {
> + break;
> + }
> +
> + /* Allocate some space for the rule */
> + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> + res[nentries - 1].flags = 0;
> +
> + if (strstart(map, "client", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
> + } else if (strstart(map, "server", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
> + } else if (strstart(map, "all", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
> + } else {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Unexpected scope;"
> + " Expecting 'client', 'server', or 'all', in rule %zu\n",
> + __func__, nentries);
> + exit(1);
> + }
> +
> +
> + if (*map != sep) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Expecting '%c' found '%c'"
> + " after scope in rule %zu\n",
> + __func__, sep, *map, nentries + 1);
> + exit(1);
> + }
> + /* Skip the separator, now at the start of the 'type' */
> + map++;
> +
> + /* Start of 'type' */
> + if (strstart(map, "prefix", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
> + } else if (strstart(map, "ok", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
> + } else if (strstart(map, "bad", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
> + } else {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Unexpected type;"
> + "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> + __func__, nentries);
> + exit(1);
> + }
> +
> + if (*map++ != sep) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of type field of rule %zu\n",
> + __func__, sep, nentries);
> + exit(1);
> + }
> +
> + /* At start of 'key' field */
> + tmp = strchr(map, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of key field of rule %zu",
> + __func__, sep, nentries);
> + exit(1);
> + }
> + res[nentries - 1].key = g_strndup(map, tmp - map);
> + map = tmp + 1;
> +
> + /* At start of 'prepend' field */
> + tmp = strchr(map, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of prepend field of rule %zu",
> + __func__, sep, nentries);
> + exit(1);
> + }
> + res[nentries - 1].prepend = g_strndup(map, tmp - map);
> + map = tmp + 1;
> + /* End of rule - go around again for another rule */
> + }
> +
> + if (!nentries) {
> + fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
> + exit(1);
> + }
> +
> + /* Add a terminator to error in cases the user hasn't specified */
> + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> + res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
> + res[nentries - 1].key = g_strdup("");
> + res[nentries - 1].prepend = g_strdup("");
> +
> + return res;
> +}
> +
> static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
> size_t size)
> {
> @@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
> } else {
> lo.source = strdup("/");
> }
> +
> + if (lo.xattrmap) {
> + xattr_map_list = parse_xattrmap(lo.xattrmap);
> + }
> +
> if (!lo.timeout_set) {
> switch (lo.cache) {
> case CACHE_NONE:
> --
> 2.26.2
>
> _______________________________________________
> Virtio-fs mailing list
> Virtio-fs@redhat.com
> https://www.redhat.com/mailman/listinfo/virtio-fs
^ permalink raw reply [flat|nested] 41+ messages in thread* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
@ 2020-09-11 21:13 ` Vivek Goyal
0 siblings, 0 replies; 41+ messages in thread
From: Vivek Goyal @ 2020-09-11 21:13 UTC (permalink / raw)
To: Dr. David Alan Gilbert (git); +Cc: virtio-fs, qemu-devel, stefanha
On Thu, Aug 27, 2020 at 04:36:54PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> Add an option to define mappings of xattr names so that
> the client and server filesystems see different views.
> This can be used to have different SELinux mappings as
> seen by the guest, to run the virtiofsd with less privileges
> (e.g. in a case where it can't set trusted/system/security
> xattrs but you want the guest to be able to), or to isolate
> multiple users of the same name; e.g. trusted attributes
> used by stacking overlayfs.
>
> A mapping engine is used wit 3 simple rules; the rules can
> be combined to allow most useful mapping scenarios.
> The ruleset is defined by -o xattrmap='rules...'.
>
> This patch doesn't use the rule maps yet.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> docs/tools/virtiofsd.rst | 55 ++++++++++++
> tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> 2 files changed, 203 insertions(+)
>
> diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> index 824e713491..2efa16d3c5 100644
> --- a/docs/tools/virtiofsd.rst
> +++ b/docs/tools/virtiofsd.rst
> @@ -107,6 +107,60 @@ Options
> performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> timeout. ``always`` sets a long cache lifetime at the expense of coherency.
>
> +xattr-mapping
> +-------------
> +
> +By default the name of xattr's used by the client are passed through to the server
> +file system. This can be a problem where either those xattr names are used
> +by something on the server (e.g. selinux client/server confusion) or if the
> +virtiofsd is running in a container with restricted priviliges where it cannot
> +access some attributes.
> +
> +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> +string consists of a series of rules.
> +
> +The first matching rule terminates the mapping.
> +
> +Each rule consists of a number of fields separated with a separator that is the
> +first non-white space character in the rule. This separator must then be used
> +for the whole rule.
> +White space may be added before and after each rule.
> +Using ':' as the separator a rule is of the form:
> +
> +``:scope:type:key:prepend:``
Hi David,
This seems very genric and which makes it harder to understand and
harder to write rules. I am wondering do we really need this degree
of flexibility. Is it worth, dropping some of the requirements
and simplify the syntax.
- I am wonderig why do we need to allow choice of separator.
- Wondering why do we need to allow separate rules for client/server.
Once we start remapping something, is it not good enough that
mapping be bidirectonal.
- Not sure why separate notion of "bad". To me once we decide to
remap something, should automatically block unprefixed version.
IOW, what functionality we will lose if we just say
-o remap_xattr="trusted.".
This implies following.
A. If client is sending any xattr prefixed with "trusted.", prefix it
with "user.virtiofs".
B. Server filters out anything starting with "trusted."
C. If server sees "user.virtiofs.trusted." it strips "user.virtiofs".
For remapping security.selinux, user could specify.
-o remap_xattr="security.selinux."
For nested configuration. virtiofsd at L1 will specify.
-o remap_xattr="security.selinux.".
And virtiofsd at L0 can specify.
-o remap_xattr="user.virtiofs.security.selinux."
I doubt we need to care about being able to remap xattrs of
other filesystems like virtio-9p.
I also have some questions about how this will be used.
Overlay
-------
- So for non nested guests, we can have two instances of overlay. Lets
call these ovl0 and ovl1. (ovl0 being on host, and ovl1 being inside
guest). Fs hierarcy might look as follows.
ext4-->ovl0-->virtiofsd0-->ovl1
This case does not work by default even if virtiofsd has CAP_SYS_ADMIN
by default as overlay does not allow nesting. So when ovl1 tries to
set trusted.overlay, ovl0 will deny it.
We could simple pass extra directory from host which does not go through
overlay on host and use that as upper inside guest.
ext4-->ovl0-->virtiofsd0-->ovl1
ext4-->ovl0/upper-->virtiofsd0-->ovl1
(/upper used as upper directory of ovl1)
I guess remapping "trusted.overlay" will allow us not to have a separate
ovl0/upper. And following itself will work. Have you tested it? Does
this work. Basically we are creating nested overlay configuration with
virtiofs in between. Is "trusted.overlay" only conflict. I wonder
there might be others. Just that "trusted.overlay" is first failure
we noticed.
Nested Overlay
--------------
- For now I will assume that we are using separate upper dir.
ext4-->ovl0-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2
ext4-->ovl0/upper1-->virtiofsd0-->ovl1(uses upper1 as upperdir)
ext4-->ovl0/upper2-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2 (users upper2
as upper dir)
Basically create two directories upper1 and upper2 on regular filesystem
say ext4/xfs. Bind mount them on ovl0/upper1 and ovl0/upper2 respectively.
And now ovl1 uses ovl0/upper1 as upperdir and ovl2 uses ovl0/upper2 as
upperdir. This should make sure ovl0, ovl1 and ovl2 are not nested from
sharing upper perspective.
Now virtiofsd1 will run with '-o remap_xattr="trusted.overlay"' and
virtiofsd0 will run with '-o remap_xattr="user.virtiofs.trusted.overlay"'
Just trying to wrap my head around how our use cases will use this new
remapping xattr thing.
Thanks
Vivek
> +
> +**scope** is:
> +
> +- 'client' - match 'key' against a xattr name from the client for
> + setxattr/getxattr/removexattr
> +- 'server' - match 'prepend' against a xattr name from the server
> + for listxattr
> +- 'all' - can be used to match both cases.
> +
> +**type** is one of:
> +
> +- 'prefix' - If 'key' matches the client then the 'prepend'
> + is added before the name is passed to the server.
> + For a server case, the prepend is tested and stripped
> + if matching.
> +
> +- 'ok' - The attribute name is OK and passed through to
> + the server unchanged.
> +
> +- 'bad' - If a client tries to use this name it's
> + denied using EPERM; when the server passes an attribute
> + name matching it's hidden.
> +
> +**key** is a string tested as a prefix on an attribute name originating
> +on the client. It maybe empty in which case a 'client' rule
> +will always match on client names.
> +
> +**prepend** is a string tested as a prefix on an attribute name originiating
> +on the server, and used as a new prefix. It maybe empty
> +in which case a 'server' rule will always match on all names from
> +the server.
> +
> +
> Examples
> --------
>
> @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> -numa node,memdev=mem \
> ...
> guest# mount -t virtiofs myfs /mnt
> +
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 083d17a960..00e96a10cd 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -64,6 +64,7 @@
> #include <syslog.h>
> #include <unistd.h>
>
> +#include "qemu/cutils.h"
> #include "passthrough_helpers.h"
> #include "passthrough_seccomp.h"
>
> @@ -144,6 +145,7 @@ struct lo_data {
> int flock;
> int posix_lock;
> int xattr;
> + char *xattrmap;
> char *source;
> char *modcaps;
> double timeout;
> @@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
> { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> { "xattr", offsetof(struct lo_data, xattr), 1 },
> { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> + { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
> { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
> { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
> @@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> fuse_reply_err(req, res == -1 ? errno : 0);
> }
>
> +typedef struct xattr_map_entry {
> + const char *key;
> + const char *prepend;
> + unsigned int flags;
> +} XattrMapEntry;
> +
> +/*
> + * Exit; process attribute unmodified if matched.
> + * An empty key applies to all.
> + */
> +#define XATTR_MAP_FLAG_END_OK (1 << 0)
> +/*
> + * The attribute is unwanted;
> + * EPERM on write hidden on read.
> + */
> +#define XATTR_MAP_FLAG_END_BAD (1 << 1)
> +/*
> + * For attr that start with 'key' prepend 'prepend'
> + * 'key' maybe empty to prepend for all attrs
> + * key is defined from set/remove point of view.
> + * Automatically reversed on read
> + */
> +#define XATTR_MAP_FLAG_PREFIX (1 << 2)
> +/* Apply rule to get/set/remove */
> +#define XATTR_MAP_FLAG_CLIENT (1 << 16)
> +/* Apply rule to list */
> +#define XATTR_MAP_FLAG_SERVER (1 << 17)
> +/* Apply rule to all */
> +#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
> +
> +static XattrMapEntry *xattr_map_list;
> +
> +static XattrMapEntry *parse_xattrmap(const char *map)
> +{
> + XattrMapEntry *res = NULL;
> + size_t nentries = 0;
> + const char *tmp;
> +
> + while (*map) {
> + char sep;
> +
> + if (isspace(*map)) {
> + map++;
> + continue;
> + }
> + /* The separator is the first non-space of the rule */
> + sep = *map++;
> + if (!sep) {
> + break;
> + }
> +
> + /* Allocate some space for the rule */
> + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> + res[nentries - 1].flags = 0;
> +
> + if (strstart(map, "client", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
> + } else if (strstart(map, "server", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
> + } else if (strstart(map, "all", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
> + } else {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Unexpected scope;"
> + " Expecting 'client', 'server', or 'all', in rule %zu\n",
> + __func__, nentries);
> + exit(1);
> + }
> +
> +
> + if (*map != sep) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Expecting '%c' found '%c'"
> + " after scope in rule %zu\n",
> + __func__, sep, *map, nentries + 1);
> + exit(1);
> + }
> + /* Skip the separator, now at the start of the 'type' */
> + map++;
> +
> + /* Start of 'type' */
> + if (strstart(map, "prefix", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
> + } else if (strstart(map, "ok", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
> + } else if (strstart(map, "bad", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
> + } else {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Unexpected type;"
> + "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> + __func__, nentries);
> + exit(1);
> + }
> +
> + if (*map++ != sep) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of type field of rule %zu\n",
> + __func__, sep, nentries);
> + exit(1);
> + }
> +
> + /* At start of 'key' field */
> + tmp = strchr(map, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of key field of rule %zu",
> + __func__, sep, nentries);
> + exit(1);
> + }
> + res[nentries - 1].key = g_strndup(map, tmp - map);
> + map = tmp + 1;
> +
> + /* At start of 'prepend' field */
> + tmp = strchr(map, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of prepend field of rule %zu",
> + __func__, sep, nentries);
> + exit(1);
> + }
> + res[nentries - 1].prepend = g_strndup(map, tmp - map);
> + map = tmp + 1;
> + /* End of rule - go around again for another rule */
> + }
> +
> + if (!nentries) {
> + fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
> + exit(1);
> + }
> +
> + /* Add a terminator to error in cases the user hasn't specified */
> + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> + res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
> + res[nentries - 1].key = g_strdup("");
> + res[nentries - 1].prepend = g_strdup("");
> +
> + return res;
> +}
> +
> static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
> size_t size)
> {
> @@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
> } else {
> lo.source = strdup("/");
> }
> +
> + if (lo.xattrmap) {
> + xattr_map_list = parse_xattrmap(lo.xattrmap);
> + }
> +
> if (!lo.timeout_set) {
> switch (lo.cache) {
> case CACHE_NONE:
> --
> 2.26.2
>
> _______________________________________________
> Virtio-fs mailing list
> Virtio-fs@redhat.com
> https://www.redhat.com/mailman/listinfo/virtio-fs
^ permalink raw reply [flat|nested] 41+ messages in thread* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
2020-09-11 21:13 ` Vivek Goyal
@ 2020-09-18 17:38 ` Dr. David Alan Gilbert
-1 siblings, 0 replies; 41+ messages in thread
From: Dr. David Alan Gilbert @ 2020-09-18 17:38 UTC (permalink / raw)
To: Vivek Goyal; +Cc: virtio-fs, qemu-devel
* Vivek Goyal (vgoyal@redhat.com) wrote:
> On Thu, Aug 27, 2020 at 04:36:54PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Add an option to define mappings of xattr names so that
> > the client and server filesystems see different views.
> > This can be used to have different SELinux mappings as
> > seen by the guest, to run the virtiofsd with less privileges
> > (e.g. in a case where it can't set trusted/system/security
> > xattrs but you want the guest to be able to), or to isolate
> > multiple users of the same name; e.g. trusted attributes
> > used by stacking overlayfs.
> >
> > A mapping engine is used wit 3 simple rules; the rules can
> > be combined to allow most useful mapping scenarios.
> > The ruleset is defined by -o xattrmap='rules...'.
> >
> > This patch doesn't use the rule maps yet.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> > docs/tools/virtiofsd.rst | 55 ++++++++++++
> > tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> > 2 files changed, 203 insertions(+)
> >
> > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> > index 824e713491..2efa16d3c5 100644
> > --- a/docs/tools/virtiofsd.rst
> > +++ b/docs/tools/virtiofsd.rst
> > @@ -107,6 +107,60 @@ Options
> > performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> > timeout. ``always`` sets a long cache lifetime at the expense of coherency.
> >
> > +xattr-mapping
> > +-------------
> > +
> > +By default the name of xattr's used by the client are passed through to the server
> > +file system. This can be a problem where either those xattr names are used
> > +by something on the server (e.g. selinux client/server confusion) or if the
> > +virtiofsd is running in a container with restricted priviliges where it cannot
> > +access some attributes.
> > +
> > +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> > +string consists of a series of rules.
> > +
> > +The first matching rule terminates the mapping.
> > +
> > +Each rule consists of a number of fields separated with a separator that is the
> > +first non-white space character in the rule. This separator must then be used
> > +for the whole rule.
> > +White space may be added before and after each rule.
> > +Using ':' as the separator a rule is of the form:
> > +
> > +``:scope:type:key:prepend:``
>
> Hi David,
>
> This seems very genric and which makes it harder to understand and
> harder to write rules. I am wondering do we really need this degree
> of flexibility. Is it worth, dropping some of the requirements
> and simplify the syntax.
I'm wondering perhaps if we could solve this by adding sugared simple
versions but leaving the flexible syntax for those who need it.
> - I am wonderig why do we need to allow choice of separator.
I didnd't have that at first, but it was simple to add and solves
the problem of if you have the separator in the string you want to
substitute.
> - Wondering why do we need to allow separate rules for client/server.
> Once we start remapping something, is it not good enough that
> mapping be bidirectonal.
>
> - Not sure why separate notion of "bad". To me once we decide to
> remap something, should automatically block unprefixed version.
I wanted to be able to block things rather than remap; for example
just to block 'trusted.'
> IOW, what functionality we will lose if we just say
>
> -o remap_xattr="trusted.".
>
> This implies following.
>
> A. If client is sending any xattr prefixed with "trusted.", prefix it
> with "user.virtiofs".
>
> B. Server filters out anything starting with "trusted."
>
> C. If server sees "user.virtiofs.trusted." it strips "user.virtiofs".
Don't forget you also have to stop the client explicitly sending
'user.virtiofs.trusted'; that would let an unpriv client process
overwrite the prefixed name.
> For remapping security.selinux, user could specify.
>
> -o remap_xattr="security.selinux."
>
> For nested configuration. virtiofsd at L1 will specify.
>
> -o remap_xattr="security.selinux.".
>
> And virtiofsd at L0 can specify.
>
> -o remap_xattr="user.virtiofs.security.selinux."
I think you're saying that means it needs to know if it's L0 or L1
which is a shame; ideally you'd be able to have something that
transparently worked at either.
In your scheme how do I do both the 'trusted.' and 'security.selinux.'
stuff?
> I doubt we need to care about being able to remap xattrs of
> other filesystems like virtio-9p.
Well that's the thing; there's at least 9p and crosvm's setup; both
of which are different, and it would make sense if someone wanted
to transition their existing on disk container to a virtiofs setup
from a 9p setup without having to change all their xattr's.
That was my main reason for wanting the flexibility.
> I also have some questions about how this will be used.
>
> Overlay
> -------
> - So for non nested guests, we can have two instances of overlay. Lets
> call these ovl0 and ovl1. (ovl0 being on host, and ovl1 being inside
> guest). Fs hierarcy might look as follows.
>
> ext4-->ovl0-->virtiofsd0-->ovl1
>
> This case does not work by default even if virtiofsd has CAP_SYS_ADMIN
> by default as overlay does not allow nesting. So when ovl1 tries to
> set trusted.overlay, ovl0 will deny it.
>
> We could simple pass extra directory from host which does not go through
> overlay on host and use that as upper inside guest.
>
> ext4-->ovl0-->virtiofsd0-->ovl1
> ext4-->ovl0/upper-->virtiofsd0-->ovl1
> (/upper used as upper directory of ovl1)
If I understand correctly that does mean that the L1 has to understand
it's an L1 and do things differently.
> I guess remapping "trusted.overlay" will allow us not to have a separate
> ovl0/upper. And following itself will work. Have you tested it? Does
> this work.
Not tried, but that is my hope.
> Basically we are creating nested overlay configuration with
> virtiofs in between. Is "trusted.overlay" only conflict. I wonder
> there might be others. Just that "trusted.overlay" is first failure
> we noticed.
I think there's a whole bunch of trusted.overlay.* stuff but I didn't
find anything else (I think jt's a define as the prefix).
Note also, that if someone has an existing fuse-overlayfs setup that
nested by using user.fuseoverlayfs you might be able to use the rule
system to map it back.
>
> Nested Overlay
> --------------
> - For now I will assume that we are using separate upper dir.
>
> ext4-->ovl0-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2
> ext4-->ovl0/upper1-->virtiofsd0-->ovl1(uses upper1 as upperdir)
> ext4-->ovl0/upper2-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2 (users upper2
> as upper dir)
>
> Basically create two directories upper1 and upper2 on regular filesystem
> say ext4/xfs. Bind mount them on ovl0/upper1 and ovl0/upper2 respectively.
> And now ovl1 uses ovl0/upper1 as upperdir and ovl2 uses ovl0/upper2 as
> upperdir. This should make sure ovl0, ovl1 and ovl2 are not nested from
> sharing upper perspective.
>
> Now virtiofsd1 will run with '-o remap_xattr="trusted.overlay"' and
> virtiofsd0 will run with '-o remap_xattr="user.virtiofs.trusted.overlay"'
You could tell both layers the same thing; prefix/strip everything with
user.virtiofs. and then you can do the same thing at both layers and
they don't need to know which layer they're at.
Dave
> Just trying to wrap my head around how our use cases will use this new
> remapping xattr thing.
>
> Thanks
> Vivek
>
>
>
> > +
> > +**scope** is:
> > +
> > +- 'client' - match 'key' against a xattr name from the client for
> > + setxattr/getxattr/removexattr
> > +- 'server' - match 'prepend' against a xattr name from the server
> > + for listxattr
> > +- 'all' - can be used to match both cases.
> > +
> > +**type** is one of:
> > +
> > +- 'prefix' - If 'key' matches the client then the 'prepend'
> > + is added before the name is passed to the server.
> > + For a server case, the prepend is tested and stripped
> > + if matching.
> > +
> > +- 'ok' - The attribute name is OK and passed through to
> > + the server unchanged.
> > +
> > +- 'bad' - If a client tries to use this name it's
> > + denied using EPERM; when the server passes an attribute
> > + name matching it's hidden.
> > +
> > +**key** is a string tested as a prefix on an attribute name originating
> > +on the client. It maybe empty in which case a 'client' rule
> > +will always match on client names.
> > +
> > +**prepend** is a string tested as a prefix on an attribute name originiating
> > +on the server, and used as a new prefix. It maybe empty
> > +in which case a 'server' rule will always match on all names from
> > +the server.
> > +
> > +
> > Examples
> > --------
> >
> > @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> > -numa node,memdev=mem \
> > ...
> > guest# mount -t virtiofs myfs /mnt
> > +
> > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> > index 083d17a960..00e96a10cd 100644
> > --- a/tools/virtiofsd/passthrough_ll.c
> > +++ b/tools/virtiofsd/passthrough_ll.c
> > @@ -64,6 +64,7 @@
> > #include <syslog.h>
> > #include <unistd.h>
> >
> > +#include "qemu/cutils.h"
> > #include "passthrough_helpers.h"
> > #include "passthrough_seccomp.h"
> >
> > @@ -144,6 +145,7 @@ struct lo_data {
> > int flock;
> > int posix_lock;
> > int xattr;
> > + char *xattrmap;
> > char *source;
> > char *modcaps;
> > double timeout;
> > @@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
> > { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> > { "xattr", offsetof(struct lo_data, xattr), 1 },
> > { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> > + { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
> > { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
> > { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> > { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
> > @@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> > fuse_reply_err(req, res == -1 ? errno : 0);
> > }
> >
> > +typedef struct xattr_map_entry {
> > + const char *key;
> > + const char *prepend;
> > + unsigned int flags;
> > +} XattrMapEntry;
> > +
> > +/*
> > + * Exit; process attribute unmodified if matched.
> > + * An empty key applies to all.
> > + */
> > +#define XATTR_MAP_FLAG_END_OK (1 << 0)
> > +/*
> > + * The attribute is unwanted;
> > + * EPERM on write hidden on read.
> > + */
> > +#define XATTR_MAP_FLAG_END_BAD (1 << 1)
> > +/*
> > + * For attr that start with 'key' prepend 'prepend'
> > + * 'key' maybe empty to prepend for all attrs
> > + * key is defined from set/remove point of view.
> > + * Automatically reversed on read
> > + */
> > +#define XATTR_MAP_FLAG_PREFIX (1 << 2)
> > +/* Apply rule to get/set/remove */
> > +#define XATTR_MAP_FLAG_CLIENT (1 << 16)
> > +/* Apply rule to list */
> > +#define XATTR_MAP_FLAG_SERVER (1 << 17)
> > +/* Apply rule to all */
> > +#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
> > +
> > +static XattrMapEntry *xattr_map_list;
> > +
> > +static XattrMapEntry *parse_xattrmap(const char *map)
> > +{
> > + XattrMapEntry *res = NULL;
> > + size_t nentries = 0;
> > + const char *tmp;
> > +
> > + while (*map) {
> > + char sep;
> > +
> > + if (isspace(*map)) {
> > + map++;
> > + continue;
> > + }
> > + /* The separator is the first non-space of the rule */
> > + sep = *map++;
> > + if (!sep) {
> > + break;
> > + }
> > +
> > + /* Allocate some space for the rule */
> > + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> > + res[nentries - 1].flags = 0;
> > +
> > + if (strstart(map, "client", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
> > + } else if (strstart(map, "server", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
> > + } else if (strstart(map, "all", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
> > + } else {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Unexpected scope;"
> > + " Expecting 'client', 'server', or 'all', in rule %zu\n",
> > + __func__, nentries);
> > + exit(1);
> > + }
> > +
> > +
> > + if (*map != sep) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Expecting '%c' found '%c'"
> > + " after scope in rule %zu\n",
> > + __func__, sep, *map, nentries + 1);
> > + exit(1);
> > + }
> > + /* Skip the separator, now at the start of the 'type' */
> > + map++;
> > +
> > + /* Start of 'type' */
> > + if (strstart(map, "prefix", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
> > + } else if (strstart(map, "ok", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
> > + } else if (strstart(map, "bad", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
> > + } else {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Unexpected type;"
> > + "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> > + __func__, nentries);
> > + exit(1);
> > + }
> > +
> > + if (*map++ != sep) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of type field of rule %zu\n",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > +
> > + /* At start of 'key' field */
> > + tmp = strchr(map, sep);
> > + if (!tmp) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of key field of rule %zu",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > + res[nentries - 1].key = g_strndup(map, tmp - map);
> > + map = tmp + 1;
> > +
> > + /* At start of 'prepend' field */
> > + tmp = strchr(map, sep);
> > + if (!tmp) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of prepend field of rule %zu",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > + res[nentries - 1].prepend = g_strndup(map, tmp - map);
> > + map = tmp + 1;
> > + /* End of rule - go around again for another rule */
> > + }
> > +
> > + if (!nentries) {
> > + fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
> > + exit(1);
> > + }
> > +
> > + /* Add a terminator to error in cases the user hasn't specified */
> > + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> > + res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
> > + res[nentries - 1].key = g_strdup("");
> > + res[nentries - 1].prepend = g_strdup("");
> > +
> > + return res;
> > +}
> > +
> > static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
> > size_t size)
> > {
> > @@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
> > } else {
> > lo.source = strdup("/");
> > }
> > +
> > + if (lo.xattrmap) {
> > + xattr_map_list = parse_xattrmap(lo.xattrmap);
> > + }
> > +
> > if (!lo.timeout_set) {
> > switch (lo.cache) {
> > case CACHE_NONE:
> > --
> > 2.26.2
> >
> > _______________________________________________
> > Virtio-fs mailing list
> > Virtio-fs@redhat.com
> > https://www.redhat.com/mailman/listinfo/virtio-fs
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 41+ messages in thread* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
@ 2020-09-18 17:38 ` Dr. David Alan Gilbert
0 siblings, 0 replies; 41+ messages in thread
From: Dr. David Alan Gilbert @ 2020-09-18 17:38 UTC (permalink / raw)
To: Vivek Goyal; +Cc: virtio-fs, qemu-devel, stefanha
* Vivek Goyal (vgoyal@redhat.com) wrote:
> On Thu, Aug 27, 2020 at 04:36:54PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Add an option to define mappings of xattr names so that
> > the client and server filesystems see different views.
> > This can be used to have different SELinux mappings as
> > seen by the guest, to run the virtiofsd with less privileges
> > (e.g. in a case where it can't set trusted/system/security
> > xattrs but you want the guest to be able to), or to isolate
> > multiple users of the same name; e.g. trusted attributes
> > used by stacking overlayfs.
> >
> > A mapping engine is used wit 3 simple rules; the rules can
> > be combined to allow most useful mapping scenarios.
> > The ruleset is defined by -o xattrmap='rules...'.
> >
> > This patch doesn't use the rule maps yet.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> > docs/tools/virtiofsd.rst | 55 ++++++++++++
> > tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> > 2 files changed, 203 insertions(+)
> >
> > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> > index 824e713491..2efa16d3c5 100644
> > --- a/docs/tools/virtiofsd.rst
> > +++ b/docs/tools/virtiofsd.rst
> > @@ -107,6 +107,60 @@ Options
> > performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> > timeout. ``always`` sets a long cache lifetime at the expense of coherency.
> >
> > +xattr-mapping
> > +-------------
> > +
> > +By default the name of xattr's used by the client are passed through to the server
> > +file system. This can be a problem where either those xattr names are used
> > +by something on the server (e.g. selinux client/server confusion) or if the
> > +virtiofsd is running in a container with restricted priviliges where it cannot
> > +access some attributes.
> > +
> > +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> > +string consists of a series of rules.
> > +
> > +The first matching rule terminates the mapping.
> > +
> > +Each rule consists of a number of fields separated with a separator that is the
> > +first non-white space character in the rule. This separator must then be used
> > +for the whole rule.
> > +White space may be added before and after each rule.
> > +Using ':' as the separator a rule is of the form:
> > +
> > +``:scope:type:key:prepend:``
>
> Hi David,
>
> This seems very genric and which makes it harder to understand and
> harder to write rules. I am wondering do we really need this degree
> of flexibility. Is it worth, dropping some of the requirements
> and simplify the syntax.
I'm wondering perhaps if we could solve this by adding sugared simple
versions but leaving the flexible syntax for those who need it.
> - I am wonderig why do we need to allow choice of separator.
I didnd't have that at first, but it was simple to add and solves
the problem of if you have the separator in the string you want to
substitute.
> - Wondering why do we need to allow separate rules for client/server.
> Once we start remapping something, is it not good enough that
> mapping be bidirectonal.
>
> - Not sure why separate notion of "bad". To me once we decide to
> remap something, should automatically block unprefixed version.
I wanted to be able to block things rather than remap; for example
just to block 'trusted.'
> IOW, what functionality we will lose if we just say
>
> -o remap_xattr="trusted.".
>
> This implies following.
>
> A. If client is sending any xattr prefixed with "trusted.", prefix it
> with "user.virtiofs".
>
> B. Server filters out anything starting with "trusted."
>
> C. If server sees "user.virtiofs.trusted." it strips "user.virtiofs".
Don't forget you also have to stop the client explicitly sending
'user.virtiofs.trusted'; that would let an unpriv client process
overwrite the prefixed name.
> For remapping security.selinux, user could specify.
>
> -o remap_xattr="security.selinux."
>
> For nested configuration. virtiofsd at L1 will specify.
>
> -o remap_xattr="security.selinux.".
>
> And virtiofsd at L0 can specify.
>
> -o remap_xattr="user.virtiofs.security.selinux."
I think you're saying that means it needs to know if it's L0 or L1
which is a shame; ideally you'd be able to have something that
transparently worked at either.
In your scheme how do I do both the 'trusted.' and 'security.selinux.'
stuff?
> I doubt we need to care about being able to remap xattrs of
> other filesystems like virtio-9p.
Well that's the thing; there's at least 9p and crosvm's setup; both
of which are different, and it would make sense if someone wanted
to transition their existing on disk container to a virtiofs setup
from a 9p setup without having to change all their xattr's.
That was my main reason for wanting the flexibility.
> I also have some questions about how this will be used.
>
> Overlay
> -------
> - So for non nested guests, we can have two instances of overlay. Lets
> call these ovl0 and ovl1. (ovl0 being on host, and ovl1 being inside
> guest). Fs hierarcy might look as follows.
>
> ext4-->ovl0-->virtiofsd0-->ovl1
>
> This case does not work by default even if virtiofsd has CAP_SYS_ADMIN
> by default as overlay does not allow nesting. So when ovl1 tries to
> set trusted.overlay, ovl0 will deny it.
>
> We could simple pass extra directory from host which does not go through
> overlay on host and use that as upper inside guest.
>
> ext4-->ovl0-->virtiofsd0-->ovl1
> ext4-->ovl0/upper-->virtiofsd0-->ovl1
> (/upper used as upper directory of ovl1)
If I understand correctly that does mean that the L1 has to understand
it's an L1 and do things differently.
> I guess remapping "trusted.overlay" will allow us not to have a separate
> ovl0/upper. And following itself will work. Have you tested it? Does
> this work.
Not tried, but that is my hope.
> Basically we are creating nested overlay configuration with
> virtiofs in between. Is "trusted.overlay" only conflict. I wonder
> there might be others. Just that "trusted.overlay" is first failure
> we noticed.
I think there's a whole bunch of trusted.overlay.* stuff but I didn't
find anything else (I think jt's a define as the prefix).
Note also, that if someone has an existing fuse-overlayfs setup that
nested by using user.fuseoverlayfs you might be able to use the rule
system to map it back.
>
> Nested Overlay
> --------------
> - For now I will assume that we are using separate upper dir.
>
> ext4-->ovl0-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2
> ext4-->ovl0/upper1-->virtiofsd0-->ovl1(uses upper1 as upperdir)
> ext4-->ovl0/upper2-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2 (users upper2
> as upper dir)
>
> Basically create two directories upper1 and upper2 on regular filesystem
> say ext4/xfs. Bind mount them on ovl0/upper1 and ovl0/upper2 respectively.
> And now ovl1 uses ovl0/upper1 as upperdir and ovl2 uses ovl0/upper2 as
> upperdir. This should make sure ovl0, ovl1 and ovl2 are not nested from
> sharing upper perspective.
>
> Now virtiofsd1 will run with '-o remap_xattr="trusted.overlay"' and
> virtiofsd0 will run with '-o remap_xattr="user.virtiofs.trusted.overlay"'
You could tell both layers the same thing; prefix/strip everything with
user.virtiofs. and then you can do the same thing at both layers and
they don't need to know which layer they're at.
Dave
> Just trying to wrap my head around how our use cases will use this new
> remapping xattr thing.
>
> Thanks
> Vivek
>
>
>
> > +
> > +**scope** is:
> > +
> > +- 'client' - match 'key' against a xattr name from the client for
> > + setxattr/getxattr/removexattr
> > +- 'server' - match 'prepend' against a xattr name from the server
> > + for listxattr
> > +- 'all' - can be used to match both cases.
> > +
> > +**type** is one of:
> > +
> > +- 'prefix' - If 'key' matches the client then the 'prepend'
> > + is added before the name is passed to the server.
> > + For a server case, the prepend is tested and stripped
> > + if matching.
> > +
> > +- 'ok' - The attribute name is OK and passed through to
> > + the server unchanged.
> > +
> > +- 'bad' - If a client tries to use this name it's
> > + denied using EPERM; when the server passes an attribute
> > + name matching it's hidden.
> > +
> > +**key** is a string tested as a prefix on an attribute name originating
> > +on the client. It maybe empty in which case a 'client' rule
> > +will always match on client names.
> > +
> > +**prepend** is a string tested as a prefix on an attribute name originiating
> > +on the server, and used as a new prefix. It maybe empty
> > +in which case a 'server' rule will always match on all names from
> > +the server.
> > +
> > +
> > Examples
> > --------
> >
> > @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> > -numa node,memdev=mem \
> > ...
> > guest# mount -t virtiofs myfs /mnt
> > +
> > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> > index 083d17a960..00e96a10cd 100644
> > --- a/tools/virtiofsd/passthrough_ll.c
> > +++ b/tools/virtiofsd/passthrough_ll.c
> > @@ -64,6 +64,7 @@
> > #include <syslog.h>
> > #include <unistd.h>
> >
> > +#include "qemu/cutils.h"
> > #include "passthrough_helpers.h"
> > #include "passthrough_seccomp.h"
> >
> > @@ -144,6 +145,7 @@ struct lo_data {
> > int flock;
> > int posix_lock;
> > int xattr;
> > + char *xattrmap;
> > char *source;
> > char *modcaps;
> > double timeout;
> > @@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
> > { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> > { "xattr", offsetof(struct lo_data, xattr), 1 },
> > { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> > + { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
> > { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
> > { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> > { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
> > @@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> > fuse_reply_err(req, res == -1 ? errno : 0);
> > }
> >
> > +typedef struct xattr_map_entry {
> > + const char *key;
> > + const char *prepend;
> > + unsigned int flags;
> > +} XattrMapEntry;
> > +
> > +/*
> > + * Exit; process attribute unmodified if matched.
> > + * An empty key applies to all.
> > + */
> > +#define XATTR_MAP_FLAG_END_OK (1 << 0)
> > +/*
> > + * The attribute is unwanted;
> > + * EPERM on write hidden on read.
> > + */
> > +#define XATTR_MAP_FLAG_END_BAD (1 << 1)
> > +/*
> > + * For attr that start with 'key' prepend 'prepend'
> > + * 'key' maybe empty to prepend for all attrs
> > + * key is defined from set/remove point of view.
> > + * Automatically reversed on read
> > + */
> > +#define XATTR_MAP_FLAG_PREFIX (1 << 2)
> > +/* Apply rule to get/set/remove */
> > +#define XATTR_MAP_FLAG_CLIENT (1 << 16)
> > +/* Apply rule to list */
> > +#define XATTR_MAP_FLAG_SERVER (1 << 17)
> > +/* Apply rule to all */
> > +#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
> > +
> > +static XattrMapEntry *xattr_map_list;
> > +
> > +static XattrMapEntry *parse_xattrmap(const char *map)
> > +{
> > + XattrMapEntry *res = NULL;
> > + size_t nentries = 0;
> > + const char *tmp;
> > +
> > + while (*map) {
> > + char sep;
> > +
> > + if (isspace(*map)) {
> > + map++;
> > + continue;
> > + }
> > + /* The separator is the first non-space of the rule */
> > + sep = *map++;
> > + if (!sep) {
> > + break;
> > + }
> > +
> > + /* Allocate some space for the rule */
> > + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> > + res[nentries - 1].flags = 0;
> > +
> > + if (strstart(map, "client", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
> > + } else if (strstart(map, "server", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
> > + } else if (strstart(map, "all", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
> > + } else {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Unexpected scope;"
> > + " Expecting 'client', 'server', or 'all', in rule %zu\n",
> > + __func__, nentries);
> > + exit(1);
> > + }
> > +
> > +
> > + if (*map != sep) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Expecting '%c' found '%c'"
> > + " after scope in rule %zu\n",
> > + __func__, sep, *map, nentries + 1);
> > + exit(1);
> > + }
> > + /* Skip the separator, now at the start of the 'type' */
> > + map++;
> > +
> > + /* Start of 'type' */
> > + if (strstart(map, "prefix", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
> > + } else if (strstart(map, "ok", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
> > + } else if (strstart(map, "bad", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
> > + } else {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Unexpected type;"
> > + "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> > + __func__, nentries);
> > + exit(1);
> > + }
> > +
> > + if (*map++ != sep) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of type field of rule %zu\n",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > +
> > + /* At start of 'key' field */
> > + tmp = strchr(map, sep);
> > + if (!tmp) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of key field of rule %zu",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > + res[nentries - 1].key = g_strndup(map, tmp - map);
> > + map = tmp + 1;
> > +
> > + /* At start of 'prepend' field */
> > + tmp = strchr(map, sep);
> > + if (!tmp) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of prepend field of rule %zu",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > + res[nentries - 1].prepend = g_strndup(map, tmp - map);
> > + map = tmp + 1;
> > + /* End of rule - go around again for another rule */
> > + }
> > +
> > + if (!nentries) {
> > + fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
> > + exit(1);
> > + }
> > +
> > + /* Add a terminator to error in cases the user hasn't specified */
> > + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> > + res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
> > + res[nentries - 1].key = g_strdup("");
> > + res[nentries - 1].prepend = g_strdup("");
> > +
> > + return res;
> > +}
> > +
> > static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
> > size_t size)
> > {
> > @@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
> > } else {
> > lo.source = strdup("/");
> > }
> > +
> > + if (lo.xattrmap) {
> > + xattr_map_list = parse_xattrmap(lo.xattrmap);
> > + }
> > +
> > if (!lo.timeout_set) {
> > switch (lo.cache) {
> > case CACHE_NONE:
> > --
> > 2.26.2
> >
> > _______________________________________________
> > Virtio-fs mailing list
> > Virtio-fs@redhat.com
> > https://www.redhat.com/mailman/listinfo/virtio-fs
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 41+ messages in thread* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
2020-09-18 17:38 ` Dr. David Alan Gilbert
(?)
@ 2020-10-20 17:20 ` Vivek Goyal
-1 siblings, 0 replies; 41+ messages in thread
From: Vivek Goyal @ 2020-10-20 17:20 UTC (permalink / raw)
To: Dr. David Alan Gilbert; +Cc: virtio-fs, qemu-devel
On Fri, Sep 18, 2020 at 06:38:38PM +0100, Dr. David Alan Gilbert wrote:
> * Vivek Goyal (vgoyal@redhat.com) wrote:
> > On Thu, Aug 27, 2020 at 04:36:54PM +0100, Dr. David Alan Gilbert (git) wrote:
> > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > >
> > > Add an option to define mappings of xattr names so that
> > > the client and server filesystems see different views.
> > > This can be used to have different SELinux mappings as
> > > seen by the guest, to run the virtiofsd with less privileges
> > > (e.g. in a case where it can't set trusted/system/security
> > > xattrs but you want the guest to be able to), or to isolate
> > > multiple users of the same name; e.g. trusted attributes
> > > used by stacking overlayfs.
> > >
> > > A mapping engine is used wit 3 simple rules; the rules can
> > > be combined to allow most useful mapping scenarios.
> > > The ruleset is defined by -o xattrmap='rules...'.
> > >
> > > This patch doesn't use the rule maps yet.
> > >
> > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > > ---
> > > docs/tools/virtiofsd.rst | 55 ++++++++++++
> > > tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> > > 2 files changed, 203 insertions(+)
> > >
> > > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> > > index 824e713491..2efa16d3c5 100644
> > > --- a/docs/tools/virtiofsd.rst
> > > +++ b/docs/tools/virtiofsd.rst
> > > @@ -107,6 +107,60 @@ Options
> > > performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> > > timeout. ``always`` sets a long cache lifetime at the expense of coherency.
> > >
> > > +xattr-mapping
> > > +-------------
> > > +
> > > +By default the name of xattr's used by the client are passed through to the server
> > > +file system. This can be a problem where either those xattr names are used
> > > +by something on the server (e.g. selinux client/server confusion) or if the
> > > +virtiofsd is running in a container with restricted priviliges where it cannot
> > > +access some attributes.
> > > +
> > > +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> > > +string consists of a series of rules.
> > > +
> > > +The first matching rule terminates the mapping.
> > > +
> > > +Each rule consists of a number of fields separated with a separator that is the
> > > +first non-white space character in the rule. This separator must then be used
> > > +for the whole rule.
> > > +White space may be added before and after each rule.
> > > +Using ':' as the separator a rule is of the form:
> > > +
> > > +``:scope:type:key:prepend:``
> >
> > Hi David,
> >
> > This seems very genric and which makes it harder to understand and
> > harder to write rules. I am wondering do we really need this degree
> > of flexibility. Is it worth, dropping some of the requirements
> > and simplify the syntax.
>
> I'm wondering perhaps if we could solve this by adding sugared simple
> versions but leaving the flexible syntax for those who need it.
I guess fair enough. This syntax is so generic (hence complex), that
its not my first choice. But if others feel the need of such a
generic mechanism, I am not going to get in the way.
>
> > - I am wonderig why do we need to allow choice of separator.
>
> I didnd't have that at first, but it was simple to add and solves
> the problem of if you have the separator in the string you want to
> substitute.
>
> > - Wondering why do we need to allow separate rules for client/server.
> > Once we start remapping something, is it not good enough that
> > mapping be bidirectonal.
> >
> > - Not sure why separate notion of "bad". To me once we decide to
> > remap something, should automatically block unprefixed version.
>
> I wanted to be able to block things rather than remap; for example
> just to block 'trusted.'
>
> > IOW, what functionality we will lose if we just say
> >
> > -o remap_xattr="trusted.".
> >
> > This implies following.
> >
> > A. If client is sending any xattr prefixed with "trusted.", prefix it
> > with "user.virtiofs".
> >
> > B. Server filters out anything starting with "trusted."
> >
> > C. If server sees "user.virtiofs.trusted." it strips "user.virtiofs".
>
[ I had missed reading this email. Looking at it now. ]
> Don't forget you also have to stop the client explicitly sending
> 'user.virtiofs.trusted'; that would let an unpriv client process
> overwrite the prefixed name.
Fair enough. Yes, we will have to block this as part of "remap_xattr"
semantics.
>
> > For remapping security.selinux, user could specify.
> >
> > -o remap_xattr="security.selinux."
> >
> > For nested configuration. virtiofsd at L1 will specify.
> >
> > -o remap_xattr="security.selinux.".
> >
> > And virtiofsd at L0 can specify.
> >
> > -o remap_xattr="user.virtiofs.security.selinux."
>
> I think you're saying that means it needs to know if it's L0 or L1
> which is a shame; ideally you'd be able to have something that
> transparently worked at either.
I will be nice to avoid knowing level information because it is
ugly. But how to avoid it? Either don't use virtiofs in stacking
configurations. But if we have to, how to avoid it?
>
> In your scheme how do I do both the 'trusted.' and 'security.selinux.'
> stuff?
We can allow specifying multiple "remap_xattr" or allow multiple
rules in single option separted by ":".
Say -o remap_xattr="security.selinux.:trusted."
>
> > I doubt we need to care about being able to remap xattrs of
> > other filesystems like virtio-9p.
>
> Well that's the thing; there's at least 9p and crosvm's setup; both
> of which are different, and it would make sense if someone wanted
> to transition their existing on disk container to a virtiofs setup
> from a 9p setup without having to change all their xattr's.
> That was my main reason for wanting the flexibility.
>
> > I also have some questions about how this will be used.
> >
> > Overlay
> > -------
> > - So for non nested guests, we can have two instances of overlay. Lets
> > call these ovl0 and ovl1. (ovl0 being on host, and ovl1 being inside
> > guest). Fs hierarcy might look as follows.
> >
> > ext4-->ovl0-->virtiofsd0-->ovl1
> >
> > This case does not work by default even if virtiofsd has CAP_SYS_ADMIN
> > by default as overlay does not allow nesting. So when ovl1 tries to
> > set trusted.overlay, ovl0 will deny it.
> >
> > We could simple pass extra directory from host which does not go through
> > overlay on host and use that as upper inside guest.
> >
> > ext4-->ovl0-->virtiofsd0-->ovl1
> > ext4-->ovl0/upper-->virtiofsd0-->ovl1
> > (/upper used as upper directory of ovl1)
>
> If I understand correctly that does mean that the L1 has to understand
> it's an L1 and do things differently.
Yes. I could not find a way to avoid it.
>
> > I guess remapping "trusted.overlay" will allow us not to have a separate
> > ovl0/upper. And following itself will work. Have you tested it? Does
> > this work.
>
> Not tried, but that is my hope.
>
> > Basically we are creating nested overlay configuration with
> > virtiofs in between. Is "trusted.overlay" only conflict. I wonder
> > there might be others. Just that "trusted.overlay" is first failure
> > we noticed.
>
> I think there's a whole bunch of trusted.overlay.* stuff but I didn't
> find anything else (I think jt's a define as the prefix).
> Note also, that if someone has an existing fuse-overlayfs setup that
> nested by using user.fuseoverlayfs you might be able to use the rule
> system to map it back.
>
> >
> > Nested Overlay
> > --------------
> > - For now I will assume that we are using separate upper dir.
> >
> > ext4-->ovl0-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2
> > ext4-->ovl0/upper1-->virtiofsd0-->ovl1(uses upper1 as upperdir)
> > ext4-->ovl0/upper2-->virtiofsd0-->ovl1-->virtiofsd1-->ovl2 (users upper2
> > as upper dir)
> >
> > Basically create two directories upper1 and upper2 on regular filesystem
> > say ext4/xfs. Bind mount them on ovl0/upper1 and ovl0/upper2 respectively.
> > And now ovl1 uses ovl0/upper1 as upperdir and ovl2 uses ovl0/upper2 as
> > upperdir. This should make sure ovl0, ovl1 and ovl2 are not nested from
> > sharing upper perspective.
> >
> > Now virtiofsd1 will run with '-o remap_xattr="trusted.overlay"' and
> > virtiofsd0 will run with '-o remap_xattr="user.virtiofs.trusted.overlay"'
>
> You could tell both layers the same thing; prefix/strip everything with
> user.virtiofs. and then you can do the same thing at both layers and
> they don't need to know which layer they're at.
Right that should work. But this will prefix user.virtiofs for every
xattr. If we want to prefix it on a specific xattr, then it become
little more tricky. Because inner most layer will do
setxattr(trusted.foo.) and next layer will do
setxattr(user.virtiofs.trusted.foo). So question is what's the common
syntax which works for both.
I have been thinking little more of nested overlay use case.
If we make sure that "upper" for each overlay instance is
separate (and not coming from stacked overlay), then following should
work well for nested configurations.
To reiterate, I think something like this should work for nested
overlay configuration.
- On host, create lower0, upper0, upper1 and upper2 dirs.
mkdir -p lower0 lower0/lower1 work0 upper1 work1 upper2 work2 ovl0
- Create ovl0 on host (L0)
mount -t overlay -o lowerdir=lower0,upperdir=upper0,workdir=work0 none ovl0
- Bind mount upper and work dirs for ovl1 and ovl2.
mkdir -p ovl0/upper1 ovl0/work1 ovl0/upper2 ovl0/work2
mount --bind upper1 ovl0/upper1
mount --bind work1 ovl0/work1
mount --bind upper2 ovl0/upper2
mount --bind work2 ovl0/work2
- Run virtiofsd0 on ovl0 with "-o remap_xattr="trusted.overlay."
- Inside L1 guest say ovl0 is mounted at "/". Create second overlay.
mkdir ovl1
mount -t overlay -o lowerdir=lower1,upperdir=upper1,workdir=work1 none ovl1
- Bind mount upper2 and work2 inside ovl1.
mkdir -p ovl1/upper2 ovl1/work2
mount --bind upper2 ovl1/upper2
mount --bind work2 ovl1/work2
- Run virtiofsd1 on ovl1 with -o "remap_xattr="trusted.overlay."
- Inisde L2 guest say virtiofs is mounted at "/"
mkdir ovl2
mount -t overlay -o lowerdir=lower1,upperdir=upper2,workdir=work2 none ovl2
Now upper for overlayfs are not stacked through overlayfs file systems.
Thanks
Vivek
^ permalink raw reply [flat|nested] 41+ messages in thread
* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
2020-08-27 15:36 ` Dr. David Alan Gilbert (git)
@ 2020-10-06 15:51 ` Christophe de Dinechin
-1 siblings, 0 replies; 41+ messages in thread
From: Christophe de Dinechin @ 2020-10-06 15:51 UTC (permalink / raw)
To: Dr. David Alan Gilbert (git); +Cc: virtio-fs, vgoyal, qemu-devel
On 2020-08-27 at 17:36 CEST, Dr. David Alan Gilbert (git) wrote...
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> Add an option to define mappings of xattr names so that
> the client and server filesystems see different views.
> This can be used to have different SELinux mappings as
> seen by the guest, to run the virtiofsd with less privileges
> (e.g. in a case where it can't set trusted/system/security
> xattrs but you want the guest to be able to), or to isolate
> multiple users of the same name; e.g. trusted attributes
> used by stacking overlayfs.
>
> A mapping engine is used wit 3 simple rules; the rules can
> be combined to allow most useful mapping scenarios.
> The ruleset is defined by -o xattrmap='rules...'.
>
> This patch doesn't use the rule maps yet.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> docs/tools/virtiofsd.rst | 55 ++++++++++++
> tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> 2 files changed, 203 insertions(+)
>
> diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> index 824e713491..2efa16d3c5 100644
> --- a/docs/tools/virtiofsd.rst
> +++ b/docs/tools/virtiofsd.rst
> @@ -107,6 +107,60 @@ Options
> performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> timeout. ``always`` sets a long cache lifetime at the expense of coherency.
>
> +xattr-mapping
> +-------------
> +
> +By default the name of xattr's used by the client are passed through to the server
> +file system. This can be a problem where either those xattr names are used
> +by something on the server (e.g. selinux client/server confusion) or if the
> +virtiofsd is running in a container with restricted priviliges where it cannot
> +access some attributes.
> +
> +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> +string consists of a series of rules.
> +
> +The first matching rule terminates the mapping.
> +
> +Each rule consists of a number of fields separated with a separator that is the
> +first non-white space character in the rule. This separator must then be used
> +for the whole rule.
> +White space may be added before and after each rule.
> +Using ':' as the separator a rule is of the form:
> +
> +``:scope:type:key:prepend:``
> +
> +**scope** is:
> +
> +- 'client' - match 'key' against a xattr name from the client for
> + setxattr/getxattr/removexattr
> +- 'server' - match 'prepend' against a xattr name from the server
> + for listxattr
> +- 'all' - can be used to match both cases.
> +
> +**type** is one of:
> +
> +- 'prefix' - If 'key' matches the client then the 'prepend'
> + is added before the name is passed to the server.
> + For a server case, the prepend is tested and stripped
> + if matching.
> +
> +- 'ok' - The attribute name is OK and passed through to
> + the server unchanged.
> +
> +- 'bad' - If a client tries to use this name it's
> + denied using EPERM; when the server passes an attribute
> + name matching it's hidden.
> +
> +**key** is a string tested as a prefix on an attribute name originating
> +on the client. It maybe empty in which case a 'client' rule
> +will always match on client names.
> +
> +**prepend** is a string tested as a prefix on an attribute name originiating
> +on the server, and used as a new prefix. It maybe empty
> +in which case a 'server' rule will always match on all names from
> +the server.
> +
> +
> Examples
> --------
>
> @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> -numa node,memdev=mem \
> ...
> guest# mount -t virtiofs myfs /mnt
> +
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 083d17a960..00e96a10cd 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -64,6 +64,7 @@
> #include <syslog.h>
> #include <unistd.h>
>
> +#include "qemu/cutils.h"
> #include "passthrough_helpers.h"
> #include "passthrough_seccomp.h"
>
> @@ -144,6 +145,7 @@ struct lo_data {
> int flock;
> int posix_lock;
> int xattr;
> + char *xattrmap;
Who owns that field? Should it be cleaned up in fuse_lo_data_cleanup() just like
source is?
> char *source;
> char *modcaps;
> double timeout;
> @@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
> { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> { "xattr", offsetof(struct lo_data, xattr), 1 },
> { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> + { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
> { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
> { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
> @@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> fuse_reply_err(req, res == -1 ? errno : 0);
> }
>
> +typedef struct xattr_map_entry {
> + const char *key;
> + const char *prepend;
> + unsigned int flags;
> +} XattrMapEntry;
> +
> +/*
> + * Exit; process attribute unmodified if matched.
> + * An empty key applies to all.
> + */
> +#define XATTR_MAP_FLAG_END_OK (1 << 0)
> +/*
> + * The attribute is unwanted;
> + * EPERM on write hidden on read.
> + */
> +#define XATTR_MAP_FLAG_END_BAD (1 << 1)
> +/*
> + * For attr that start with 'key' prepend 'prepend'
> + * 'key' maybe empty to prepend for all attrs
> + * key is defined from set/remove point of view.
> + * Automatically reversed on read
> + */
> +#define XATTR_MAP_FLAG_PREFIX (1 << 2)
> +/* Apply rule to get/set/remove */
> +#define XATTR_MAP_FLAG_CLIENT (1 << 16)
> +/* Apply rule to list */
> +#define XATTR_MAP_FLAG_SERVER (1 << 17)
> +/* Apply rule to all */
> +#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
> +
> +static XattrMapEntry *xattr_map_list;
Curious why you made it a static variable and not a field in struct lo_data?
> +
> +static XattrMapEntry *parse_xattrmap(const char *map)
> +{
> + XattrMapEntry *res = NULL;
> + size_t nentries = 0;
> + const char *tmp;
> +
> + while (*map) {
> + char sep;
> +
> + if (isspace(*map)) {
> + map++;
> + continue;
> + }
> + /* The separator is the first non-space of the rule */
> + sep = *map++;
> + if (!sep) {
> + break;
> + }
> +
> + /* Allocate some space for the rule */
> + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> + res[nentries - 1].flags = 0;
I would probably create an `entry` pointer to `res[nentries - 1]`
since there are 9 uses for it.
> +
> + if (strstart(map, "client", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
> + } else if (strstart(map, "server", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
> + } else if (strstart(map, "all", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
> + } else {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Unexpected scope;"
> + " Expecting 'client', 'server', or 'all', in rule %zu\n",
> + __func__, nentries);
> + exit(1);
> + }
> +
> +
> + if (*map != sep) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Expecting '%c' found '%c'"
> + " after scope in rule %zu\n",
> + __func__, sep, *map, nentries + 1);
I think it should be `nentries` here like in the others
> + exit(1);
> + }
> + /* Skip the separator, now at the start of the 'type' */
> + map++;
> +
> + /* Start of 'type' */
> + if (strstart(map, "prefix", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
> + } else if (strstart(map, "ok", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
> + } else if (strstart(map, "bad", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
> + } else {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Unexpected type;"
> + "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> + __func__, nentries);
> + exit(1);
> + }
> +
> + if (*map++ != sep) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of type field of rule %zu\n",
> + __func__, sep, nentries);
> + exit(1);
> + }
> +
> + /* At start of 'key' field */
> + tmp = strchr(map, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of key field of rule %zu",
> + __func__, sep, nentries);
> + exit(1);
> + }
> + res[nentries - 1].key = g_strndup(map, tmp - map);
> + map = tmp + 1;
> +
> + /* At start of 'prepend' field */
> + tmp = strchr(map, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of prepend field of rule %zu",
> + __func__, sep, nentries);
> + exit(1);
> + }
> + res[nentries - 1].prepend = g_strndup(map, tmp - map);
> + map = tmp + 1;
> + /* End of rule - go around again for another rule */
> + }
> +
> + if (!nentries) {
> + fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
> + exit(1);
> + }
> +
> + /* Add a terminator to error in cases the user hasn't specified */
> + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> + res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
> + res[nentries - 1].key = g_strdup("");
> + res[nentries - 1].prepend = g_strdup("");
> +
> + return res;
> +}
> +
> static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
> size_t size)
> {
> @@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
> } else {
> lo.source = strdup("/");
> }
> +
> + if (lo.xattrmap) {
> + xattr_map_list = parse_xattrmap(lo.xattrmap);
This is never freed. If you put the static in struct lo_data, you could
naturally clean it up in fuse_lo_data_cleanup.
> + }
> +
> if (!lo.timeout_set) {
> switch (lo.cache) {
> case CACHE_NONE:
--
Cheers,
Christophe de Dinechin (IRC c3d)
^ permalink raw reply [flat|nested] 41+ messages in thread* Re: [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
@ 2020-10-06 15:51 ` Christophe de Dinechin
0 siblings, 0 replies; 41+ messages in thread
From: Christophe de Dinechin @ 2020-10-06 15:51 UTC (permalink / raw)
To: Dr. David Alan Gilbert (git); +Cc: virtio-fs, stefanha, vgoyal, qemu-devel
On 2020-08-27 at 17:36 CEST, Dr. David Alan Gilbert (git) wrote...
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> Add an option to define mappings of xattr names so that
> the client and server filesystems see different views.
> This can be used to have different SELinux mappings as
> seen by the guest, to run the virtiofsd with less privileges
> (e.g. in a case where it can't set trusted/system/security
> xattrs but you want the guest to be able to), or to isolate
> multiple users of the same name; e.g. trusted attributes
> used by stacking overlayfs.
>
> A mapping engine is used wit 3 simple rules; the rules can
> be combined to allow most useful mapping scenarios.
> The ruleset is defined by -o xattrmap='rules...'.
>
> This patch doesn't use the rule maps yet.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> docs/tools/virtiofsd.rst | 55 ++++++++++++
> tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> 2 files changed, 203 insertions(+)
>
> diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> index 824e713491..2efa16d3c5 100644
> --- a/docs/tools/virtiofsd.rst
> +++ b/docs/tools/virtiofsd.rst
> @@ -107,6 +107,60 @@ Options
> performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> timeout. ``always`` sets a long cache lifetime at the expense of coherency.
>
> +xattr-mapping
> +-------------
> +
> +By default the name of xattr's used by the client are passed through to the server
> +file system. This can be a problem where either those xattr names are used
> +by something on the server (e.g. selinux client/server confusion) or if the
> +virtiofsd is running in a container with restricted priviliges where it cannot
> +access some attributes.
> +
> +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> +string consists of a series of rules.
> +
> +The first matching rule terminates the mapping.
> +
> +Each rule consists of a number of fields separated with a separator that is the
> +first non-white space character in the rule. This separator must then be used
> +for the whole rule.
> +White space may be added before and after each rule.
> +Using ':' as the separator a rule is of the form:
> +
> +``:scope:type:key:prepend:``
> +
> +**scope** is:
> +
> +- 'client' - match 'key' against a xattr name from the client for
> + setxattr/getxattr/removexattr
> +- 'server' - match 'prepend' against a xattr name from the server
> + for listxattr
> +- 'all' - can be used to match both cases.
> +
> +**type** is one of:
> +
> +- 'prefix' - If 'key' matches the client then the 'prepend'
> + is added before the name is passed to the server.
> + For a server case, the prepend is tested and stripped
> + if matching.
> +
> +- 'ok' - The attribute name is OK and passed through to
> + the server unchanged.
> +
> +- 'bad' - If a client tries to use this name it's
> + denied using EPERM; when the server passes an attribute
> + name matching it's hidden.
> +
> +**key** is a string tested as a prefix on an attribute name originating
> +on the client. It maybe empty in which case a 'client' rule
> +will always match on client names.
> +
> +**prepend** is a string tested as a prefix on an attribute name originiating
> +on the server, and used as a new prefix. It maybe empty
> +in which case a 'server' rule will always match on all names from
> +the server.
> +
> +
> Examples
> --------
>
> @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> -numa node,memdev=mem \
> ...
> guest# mount -t virtiofs myfs /mnt
> +
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 083d17a960..00e96a10cd 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -64,6 +64,7 @@
> #include <syslog.h>
> #include <unistd.h>
>
> +#include "qemu/cutils.h"
> #include "passthrough_helpers.h"
> #include "passthrough_seccomp.h"
>
> @@ -144,6 +145,7 @@ struct lo_data {
> int flock;
> int posix_lock;
> int xattr;
> + char *xattrmap;
Who owns that field? Should it be cleaned up in fuse_lo_data_cleanup() just like
source is?
> char *source;
> char *modcaps;
> double timeout;
> @@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
> { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> { "xattr", offsetof(struct lo_data, xattr), 1 },
> { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> + { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
> { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
> { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
> @@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> fuse_reply_err(req, res == -1 ? errno : 0);
> }
>
> +typedef struct xattr_map_entry {
> + const char *key;
> + const char *prepend;
> + unsigned int flags;
> +} XattrMapEntry;
> +
> +/*
> + * Exit; process attribute unmodified if matched.
> + * An empty key applies to all.
> + */
> +#define XATTR_MAP_FLAG_END_OK (1 << 0)
> +/*
> + * The attribute is unwanted;
> + * EPERM on write hidden on read.
> + */
> +#define XATTR_MAP_FLAG_END_BAD (1 << 1)
> +/*
> + * For attr that start with 'key' prepend 'prepend'
> + * 'key' maybe empty to prepend for all attrs
> + * key is defined from set/remove point of view.
> + * Automatically reversed on read
> + */
> +#define XATTR_MAP_FLAG_PREFIX (1 << 2)
> +/* Apply rule to get/set/remove */
> +#define XATTR_MAP_FLAG_CLIENT (1 << 16)
> +/* Apply rule to list */
> +#define XATTR_MAP_FLAG_SERVER (1 << 17)
> +/* Apply rule to all */
> +#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
> +
> +static XattrMapEntry *xattr_map_list;
Curious why you made it a static variable and not a field in struct lo_data?
> +
> +static XattrMapEntry *parse_xattrmap(const char *map)
> +{
> + XattrMapEntry *res = NULL;
> + size_t nentries = 0;
> + const char *tmp;
> +
> + while (*map) {
> + char sep;
> +
> + if (isspace(*map)) {
> + map++;
> + continue;
> + }
> + /* The separator is the first non-space of the rule */
> + sep = *map++;
> + if (!sep) {
> + break;
> + }
> +
> + /* Allocate some space for the rule */
> + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> + res[nentries - 1].flags = 0;
I would probably create an `entry` pointer to `res[nentries - 1]`
since there are 9 uses for it.
> +
> + if (strstart(map, "client", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
> + } else if (strstart(map, "server", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
> + } else if (strstart(map, "all", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
> + } else {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Unexpected scope;"
> + " Expecting 'client', 'server', or 'all', in rule %zu\n",
> + __func__, nentries);
> + exit(1);
> + }
> +
> +
> + if (*map != sep) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Expecting '%c' found '%c'"
> + " after scope in rule %zu\n",
> + __func__, sep, *map, nentries + 1);
I think it should be `nentries` here like in the others
> + exit(1);
> + }
> + /* Skip the separator, now at the start of the 'type' */
> + map++;
> +
> + /* Start of 'type' */
> + if (strstart(map, "prefix", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
> + } else if (strstart(map, "ok", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
> + } else if (strstart(map, "bad", &map)) {
> + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
> + } else {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Unexpected type;"
> + "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> + __func__, nentries);
> + exit(1);
> + }
> +
> + if (*map++ != sep) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of type field of rule %zu\n",
> + __func__, sep, nentries);
> + exit(1);
> + }
> +
> + /* At start of 'key' field */
> + tmp = strchr(map, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of key field of rule %zu",
> + __func__, sep, nentries);
> + exit(1);
> + }
> + res[nentries - 1].key = g_strndup(map, tmp - map);
> + map = tmp + 1;
> +
> + /* At start of 'prepend' field */
> + tmp = strchr(map, sep);
> + if (!tmp) {
> + fuse_log(FUSE_LOG_ERR,
> + "%s: Missing '%c' at end of prepend field of rule %zu",
> + __func__, sep, nentries);
> + exit(1);
> + }
> + res[nentries - 1].prepend = g_strndup(map, tmp - map);
> + map = tmp + 1;
> + /* End of rule - go around again for another rule */
> + }
> +
> + if (!nentries) {
> + fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
> + exit(1);
> + }
> +
> + /* Add a terminator to error in cases the user hasn't specified */
> + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> + res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
> + res[nentries - 1].key = g_strdup("");
> + res[nentries - 1].prepend = g_strdup("");
> +
> + return res;
> +}
> +
> static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
> size_t size)
> {
> @@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
> } else {
> lo.source = strdup("/");
> }
> +
> + if (lo.xattrmap) {
> + xattr_map_list = parse_xattrmap(lo.xattrmap);
This is never freed. If you put the static in struct lo_data, you could
naturally clean it up in fuse_lo_data_cleanup.
> + }
> +
> if (!lo.timeout_set) {
> switch (lo.cache) {
> case CACHE_NONE:
--
Cheers,
Christophe de Dinechin (IRC c3d)
^ permalink raw reply [flat|nested] 41+ messages in thread* Re: [Virtio-fs] [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
2020-10-06 15:51 ` Christophe de Dinechin
@ 2020-10-14 15:40 ` Dr. David Alan Gilbert
-1 siblings, 0 replies; 41+ messages in thread
From: Dr. David Alan Gilbert @ 2020-10-14 15:40 UTC (permalink / raw)
To: Christophe de Dinechin; +Cc: virtio-fs, vgoyal, qemu-devel
* Christophe de Dinechin (dinechin@redhat.com) wrote:
>
> On 2020-08-27 at 17:36 CEST, Dr. David Alan Gilbert (git) wrote...
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Add an option to define mappings of xattr names so that
> > the client and server filesystems see different views.
> > This can be used to have different SELinux mappings as
> > seen by the guest, to run the virtiofsd with less privileges
> > (e.g. in a case where it can't set trusted/system/security
> > xattrs but you want the guest to be able to), or to isolate
> > multiple users of the same name; e.g. trusted attributes
> > used by stacking overlayfs.
> >
> > A mapping engine is used wit 3 simple rules; the rules can
> > be combined to allow most useful mapping scenarios.
> > The ruleset is defined by -o xattrmap='rules...'.
> >
> > This patch doesn't use the rule maps yet.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> > docs/tools/virtiofsd.rst | 55 ++++++++++++
> > tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> > 2 files changed, 203 insertions(+)
> >
> > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> > index 824e713491..2efa16d3c5 100644
> > --- a/docs/tools/virtiofsd.rst
> > +++ b/docs/tools/virtiofsd.rst
> > @@ -107,6 +107,60 @@ Options
> > performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> > timeout. ``always`` sets a long cache lifetime at the expense of coherency.
> >
> > +xattr-mapping
> > +-------------
> > +
> > +By default the name of xattr's used by the client are passed through to the server
> > +file system. This can be a problem where either those xattr names are used
> > +by something on the server (e.g. selinux client/server confusion) or if the
> > +virtiofsd is running in a container with restricted priviliges where it cannot
> > +access some attributes.
> > +
> > +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> > +string consists of a series of rules.
> > +
> > +The first matching rule terminates the mapping.
> > +
> > +Each rule consists of a number of fields separated with a separator that is the
> > +first non-white space character in the rule. This separator must then be used
> > +for the whole rule.
> > +White space may be added before and after each rule.
> > +Using ':' as the separator a rule is of the form:
> > +
> > +``:scope:type:key:prepend:``
> > +
> > +**scope** is:
> > +
> > +- 'client' - match 'key' against a xattr name from the client for
> > + setxattr/getxattr/removexattr
> > +- 'server' - match 'prepend' against a xattr name from the server
> > + for listxattr
> > +- 'all' - can be used to match both cases.
> > +
> > +**type** is one of:
> > +
> > +- 'prefix' - If 'key' matches the client then the 'prepend'
> > + is added before the name is passed to the server.
> > + For a server case, the prepend is tested and stripped
> > + if matching.
> > +
> > +- 'ok' - The attribute name is OK and passed through to
> > + the server unchanged.
> > +
> > +- 'bad' - If a client tries to use this name it's
> > + denied using EPERM; when the server passes an attribute
> > + name matching it's hidden.
> > +
> > +**key** is a string tested as a prefix on an attribute name originating
> > +on the client. It maybe empty in which case a 'client' rule
> > +will always match on client names.
> > +
> > +**prepend** is a string tested as a prefix on an attribute name originiating
> > +on the server, and used as a new prefix. It maybe empty
> > +in which case a 'server' rule will always match on all names from
> > +the server.
> > +
> > +
> > Examples
> > --------
> >
> > @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> > -numa node,memdev=mem \
> > ...
> > guest# mount -t virtiofs myfs /mnt
> > +
> > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> > index 083d17a960..00e96a10cd 100644
> > --- a/tools/virtiofsd/passthrough_ll.c
> > +++ b/tools/virtiofsd/passthrough_ll.c
> > @@ -64,6 +64,7 @@
> > #include <syslog.h>
> > #include <unistd.h>
> >
> > +#include "qemu/cutils.h"
> > #include "passthrough_helpers.h"
> > #include "passthrough_seccomp.h"
> >
> > @@ -144,6 +145,7 @@ struct lo_data {
> > int flock;
> > int posix_lock;
> > int xattr;
> > + char *xattrmap;
>
> Who owns that field? Should it be cleaned up in fuse_lo_data_cleanup() just like
> source is?
Done.
> > char *source;
> > char *modcaps;
> > double timeout;
> > @@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
> > { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> > { "xattr", offsetof(struct lo_data, xattr), 1 },
> > { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> > + { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
> > { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
> > { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> > { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
> > @@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> > fuse_reply_err(req, res == -1 ? errno : 0);
> > }
> >
> > +typedef struct xattr_map_entry {
> > + const char *key;
> > + const char *prepend;
> > + unsigned int flags;
> > +} XattrMapEntry;
> > +
> > +/*
> > + * Exit; process attribute unmodified if matched.
> > + * An empty key applies to all.
> > + */
> > +#define XATTR_MAP_FLAG_END_OK (1 << 0)
> > +/*
> > + * The attribute is unwanted;
> > + * EPERM on write hidden on read.
> > + */
> > +#define XATTR_MAP_FLAG_END_BAD (1 << 1)
> > +/*
> > + * For attr that start with 'key' prepend 'prepend'
> > + * 'key' maybe empty to prepend for all attrs
> > + * key is defined from set/remove point of view.
> > + * Automatically reversed on read
> > + */
> > +#define XATTR_MAP_FLAG_PREFIX (1 << 2)
> > +/* Apply rule to get/set/remove */
> > +#define XATTR_MAP_FLAG_CLIENT (1 << 16)
> > +/* Apply rule to list */
> > +#define XATTR_MAP_FLAG_SERVER (1 << 17)
> > +/* Apply rule to all */
> > +#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
> > +
> > +static XattrMapEntry *xattr_map_list;
>
> Curious why you made it a static variable and not a field in struct lo_data?
Done.
> > +
> > +static XattrMapEntry *parse_xattrmap(const char *map)
> > +{
> > + XattrMapEntry *res = NULL;
> > + size_t nentries = 0;
> > + const char *tmp;
> > +
> > + while (*map) {
> > + char sep;
> > +
> > + if (isspace(*map)) {
> > + map++;
> > + continue;
> > + }
> > + /* The separator is the first non-space of the rule */
> > + sep = *map++;
> > + if (!sep) {
> > + break;
> > + }
> > +
> > + /* Allocate some space for the rule */
> > + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> > + res[nentries - 1].flags = 0;
>
> I would probably create an `entry` pointer to `res[nentries - 1]`
> since there are 9 uses for it.
I've reworked that whole bit; we've now got a temporary and a function
that adds an entry.
> > +
> > + if (strstart(map, "client", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
> > + } else if (strstart(map, "server", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
> > + } else if (strstart(map, "all", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
> > + } else {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Unexpected scope;"
> > + " Expecting 'client', 'server', or 'all', in rule %zu\n",
> > + __func__, nentries);
> > + exit(1);
> > + }
> > +
> > +
> > + if (*map != sep) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Expecting '%c' found '%c'"
> > + " after scope in rule %zu\n",
> > + __func__, sep, *map, nentries + 1);
>
> I think it should be `nentries` here like in the others
Done.
> > + exit(1);
> > + }
> > + /* Skip the separator, now at the start of the 'type' */
> > + map++;
> > +
> > + /* Start of 'type' */
> > + if (strstart(map, "prefix", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
> > + } else if (strstart(map, "ok", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
> > + } else if (strstart(map, "bad", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
> > + } else {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Unexpected type;"
> > + "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> > + __func__, nentries);
> > + exit(1);
> > + }
> > +
> > + if (*map++ != sep) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of type field of rule %zu\n",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > +
> > + /* At start of 'key' field */
> > + tmp = strchr(map, sep);
> > + if (!tmp) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of key field of rule %zu",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > + res[nentries - 1].key = g_strndup(map, tmp - map);
> > + map = tmp + 1;
> > +
> > + /* At start of 'prepend' field */
> > + tmp = strchr(map, sep);
> > + if (!tmp) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of prepend field of rule %zu",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > + res[nentries - 1].prepend = g_strndup(map, tmp - map);
> > + map = tmp + 1;
> > + /* End of rule - go around again for another rule */
> > + }
> > +
> > + if (!nentries) {
> > + fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
> > + exit(1);
> > + }
> > +
> > + /* Add a terminator to error in cases the user hasn't specified */
> > + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> > + res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
> > + res[nentries - 1].key = g_strdup("");
> > + res[nentries - 1].prepend = g_strdup("");
> > +
> > + return res;
> > +}
> > +
> > static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
> > size_t size)
> > {
> > @@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
> > } else {
> > lo.source = strdup("/");
> > }
> > +
> > + if (lo.xattrmap) {
> > + xattr_map_list = parse_xattrmap(lo.xattrmap);
>
> This is never freed. If you put the static in struct lo_data, you could
> naturally clean it up in fuse_lo_data_cleanup.
Cleanup added.
Dave
> > + }
> > +
> > if (!lo.timeout_set) {
> > switch (lo.cache) {
> > case CACHE_NONE:
>
>
> --
> Cheers,
> Christophe de Dinechin (IRC c3d)
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 41+ messages in thread* Re: [PATCH v2 3/6] tools/virtiofsd: xattr name mappings: Add option
@ 2020-10-14 15:40 ` Dr. David Alan Gilbert
0 siblings, 0 replies; 41+ messages in thread
From: Dr. David Alan Gilbert @ 2020-10-14 15:40 UTC (permalink / raw)
To: Christophe de Dinechin; +Cc: virtio-fs, stefanha, vgoyal, qemu-devel
* Christophe de Dinechin (dinechin@redhat.com) wrote:
>
> On 2020-08-27 at 17:36 CEST, Dr. David Alan Gilbert (git) wrote...
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > Add an option to define mappings of xattr names so that
> > the client and server filesystems see different views.
> > This can be used to have different SELinux mappings as
> > seen by the guest, to run the virtiofsd with less privileges
> > (e.g. in a case where it can't set trusted/system/security
> > xattrs but you want the guest to be able to), or to isolate
> > multiple users of the same name; e.g. trusted attributes
> > used by stacking overlayfs.
> >
> > A mapping engine is used wit 3 simple rules; the rules can
> > be combined to allow most useful mapping scenarios.
> > The ruleset is defined by -o xattrmap='rules...'.
> >
> > This patch doesn't use the rule maps yet.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> > docs/tools/virtiofsd.rst | 55 ++++++++++++
> > tools/virtiofsd/passthrough_ll.c | 148 +++++++++++++++++++++++++++++++
> > 2 files changed, 203 insertions(+)
> >
> > diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst
> > index 824e713491..2efa16d3c5 100644
> > --- a/docs/tools/virtiofsd.rst
> > +++ b/docs/tools/virtiofsd.rst
> > @@ -107,6 +107,60 @@ Options
> > performance. ``auto`` acts similar to NFS with a 1 second metadata cache
> > timeout. ``always`` sets a long cache lifetime at the expense of coherency.
> >
> > +xattr-mapping
> > +-------------
> > +
> > +By default the name of xattr's used by the client are passed through to the server
> > +file system. This can be a problem where either those xattr names are used
> > +by something on the server (e.g. selinux client/server confusion) or if the
> > +virtiofsd is running in a container with restricted priviliges where it cannot
> > +access some attributes.
> > +
> > +A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
> > +string consists of a series of rules.
> > +
> > +The first matching rule terminates the mapping.
> > +
> > +Each rule consists of a number of fields separated with a separator that is the
> > +first non-white space character in the rule. This separator must then be used
> > +for the whole rule.
> > +White space may be added before and after each rule.
> > +Using ':' as the separator a rule is of the form:
> > +
> > +``:scope:type:key:prepend:``
> > +
> > +**scope** is:
> > +
> > +- 'client' - match 'key' against a xattr name from the client for
> > + setxattr/getxattr/removexattr
> > +- 'server' - match 'prepend' against a xattr name from the server
> > + for listxattr
> > +- 'all' - can be used to match both cases.
> > +
> > +**type** is one of:
> > +
> > +- 'prefix' - If 'key' matches the client then the 'prepend'
> > + is added before the name is passed to the server.
> > + For a server case, the prepend is tested and stripped
> > + if matching.
> > +
> > +- 'ok' - The attribute name is OK and passed through to
> > + the server unchanged.
> > +
> > +- 'bad' - If a client tries to use this name it's
> > + denied using EPERM; when the server passes an attribute
> > + name matching it's hidden.
> > +
> > +**key** is a string tested as a prefix on an attribute name originating
> > +on the client. It maybe empty in which case a 'client' rule
> > +will always match on client names.
> > +
> > +**prepend** is a string tested as a prefix on an attribute name originiating
> > +on the server, and used as a new prefix. It maybe empty
> > +in which case a 'server' rule will always match on all names from
> > +the server.
> > +
> > +
> > Examples
> > --------
> >
> > @@ -123,3 +177,4 @@ Export ``/var/lib/fs/vm001/`` on vhost-user UNIX domain socket
> > -numa node,memdev=mem \
> > ...
> > guest# mount -t virtiofs myfs /mnt
> > +
> > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> > index 083d17a960..00e96a10cd 100644
> > --- a/tools/virtiofsd/passthrough_ll.c
> > +++ b/tools/virtiofsd/passthrough_ll.c
> > @@ -64,6 +64,7 @@
> > #include <syslog.h>
> > #include <unistd.h>
> >
> > +#include "qemu/cutils.h"
> > #include "passthrough_helpers.h"
> > #include "passthrough_seccomp.h"
> >
> > @@ -144,6 +145,7 @@ struct lo_data {
> > int flock;
> > int posix_lock;
> > int xattr;
> > + char *xattrmap;
>
> Who owns that field? Should it be cleaned up in fuse_lo_data_cleanup() just like
> source is?
Done.
> > char *source;
> > char *modcaps;
> > double timeout;
> > @@ -171,6 +173,7 @@ static const struct fuse_opt lo_opts[] = {
> > { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
> > { "xattr", offsetof(struct lo_data, xattr), 1 },
> > { "no_xattr", offsetof(struct lo_data, xattr), 0 },
> > + { "xattrmap=%s", offsetof(struct lo_data, xattrmap), 0 },
> > { "modcaps=%s", offsetof(struct lo_data, modcaps), 0 },
> > { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
> > { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
> > @@ -2003,6 +2006,146 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> > fuse_reply_err(req, res == -1 ? errno : 0);
> > }
> >
> > +typedef struct xattr_map_entry {
> > + const char *key;
> > + const char *prepend;
> > + unsigned int flags;
> > +} XattrMapEntry;
> > +
> > +/*
> > + * Exit; process attribute unmodified if matched.
> > + * An empty key applies to all.
> > + */
> > +#define XATTR_MAP_FLAG_END_OK (1 << 0)
> > +/*
> > + * The attribute is unwanted;
> > + * EPERM on write hidden on read.
> > + */
> > +#define XATTR_MAP_FLAG_END_BAD (1 << 1)
> > +/*
> > + * For attr that start with 'key' prepend 'prepend'
> > + * 'key' maybe empty to prepend for all attrs
> > + * key is defined from set/remove point of view.
> > + * Automatically reversed on read
> > + */
> > +#define XATTR_MAP_FLAG_PREFIX (1 << 2)
> > +/* Apply rule to get/set/remove */
> > +#define XATTR_MAP_FLAG_CLIENT (1 << 16)
> > +/* Apply rule to list */
> > +#define XATTR_MAP_FLAG_SERVER (1 << 17)
> > +/* Apply rule to all */
> > +#define XATTR_MAP_FLAG_ALL (XATTR_MAP_FLAG_SERVER | XATTR_MAP_FLAG_CLIENT)
> > +
> > +static XattrMapEntry *xattr_map_list;
>
> Curious why you made it a static variable and not a field in struct lo_data?
Done.
> > +
> > +static XattrMapEntry *parse_xattrmap(const char *map)
> > +{
> > + XattrMapEntry *res = NULL;
> > + size_t nentries = 0;
> > + const char *tmp;
> > +
> > + while (*map) {
> > + char sep;
> > +
> > + if (isspace(*map)) {
> > + map++;
> > + continue;
> > + }
> > + /* The separator is the first non-space of the rule */
> > + sep = *map++;
> > + if (!sep) {
> > + break;
> > + }
> > +
> > + /* Allocate some space for the rule */
> > + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> > + res[nentries - 1].flags = 0;
>
> I would probably create an `entry` pointer to `res[nentries - 1]`
> since there are 9 uses for it.
I've reworked that whole bit; we've now got a temporary and a function
that adds an entry.
> > +
> > + if (strstart(map, "client", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_CLIENT;
> > + } else if (strstart(map, "server", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_SERVER;
> > + } else if (strstart(map, "all", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_ALL;
> > + } else {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Unexpected scope;"
> > + " Expecting 'client', 'server', or 'all', in rule %zu\n",
> > + __func__, nentries);
> > + exit(1);
> > + }
> > +
> > +
> > + if (*map != sep) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Expecting '%c' found '%c'"
> > + " after scope in rule %zu\n",
> > + __func__, sep, *map, nentries + 1);
>
> I think it should be `nentries` here like in the others
Done.
> > + exit(1);
> > + }
> > + /* Skip the separator, now at the start of the 'type' */
> > + map++;
> > +
> > + /* Start of 'type' */
> > + if (strstart(map, "prefix", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_PREFIX;
> > + } else if (strstart(map, "ok", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_OK;
> > + } else if (strstart(map, "bad", &map)) {
> > + res[nentries - 1].flags |= XATTR_MAP_FLAG_END_BAD;
> > + } else {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Unexpected type;"
> > + "Expecting 'prefix', 'ok', or 'bad' in rule %zu\n",
> > + __func__, nentries);
> > + exit(1);
> > + }
> > +
> > + if (*map++ != sep) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of type field of rule %zu\n",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > +
> > + /* At start of 'key' field */
> > + tmp = strchr(map, sep);
> > + if (!tmp) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of key field of rule %zu",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > + res[nentries - 1].key = g_strndup(map, tmp - map);
> > + map = tmp + 1;
> > +
> > + /* At start of 'prepend' field */
> > + tmp = strchr(map, sep);
> > + if (!tmp) {
> > + fuse_log(FUSE_LOG_ERR,
> > + "%s: Missing '%c' at end of prepend field of rule %zu",
> > + __func__, sep, nentries);
> > + exit(1);
> > + }
> > + res[nentries - 1].prepend = g_strndup(map, tmp - map);
> > + map = tmp + 1;
> > + /* End of rule - go around again for another rule */
> > + }
> > +
> > + if (!nentries) {
> > + fuse_log(FUSE_LOG_ERR, "Empty xattr map\n");
> > + exit(1);
> > + }
> > +
> > + /* Add a terminator to error in cases the user hasn't specified */
> > + res = g_realloc_n(res, ++nentries, sizeof(XattrMapEntry));
> > + res[nentries - 1].flags = XATTR_MAP_FLAG_ALL | XATTR_MAP_FLAG_END_BAD;
> > + res[nentries - 1].key = g_strdup("");
> > + res[nentries - 1].prepend = g_strdup("");
> > +
> > + return res;
> > +}
> > +
> > static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
> > size_t size)
> > {
> > @@ -2909,6 +3052,11 @@ int main(int argc, char *argv[])
> > } else {
> > lo.source = strdup("/");
> > }
> > +
> > + if (lo.xattrmap) {
> > + xattr_map_list = parse_xattrmap(lo.xattrmap);
>
> This is never freed. If you put the static in struct lo_data, you could
> naturally clean it up in fuse_lo_data_cleanup.
Cleanup added.
Dave
> > + }
> > +
> > if (!lo.timeout_set) {
> > switch (lo.cache) {
> > case CACHE_NONE:
>
>
> --
> Cheers,
> Christophe de Dinechin (IRC c3d)
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
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