[PATCH v13 49/51] nfs: Distinguish missing users and groups from nobody

Andreas Gruenbacher
2015-11-03T15:23:19Z

User and group names are mapped to IDs using the kernel keyring infrastructure.
When a name does not exist, it is mapped to the nobody user or group; there is
no way to tell the difference from the mapping result.

In ACLs, we need to make that distinction. For that, use the new "xuid" and
"xgid" maps: they behave like the old "uid" and "gid" maps except that the IDs
of existing users and groups are prefixed by a "+" sign.

When the "xuid" or "xgid" maps are not supported, nfs falls back to the "uid"
and "gid" maps.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/nfs/nfs4idmap.c | 57 ++++++++++++++++++++++++++++++++++++++---------
fs/nfs/nfs4xdr.c | 6 +++--
include/linux/nfs_fs_sb.h | 1 +
3 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c
index 2e49022..34dd404 100644
--- a/fs/nfs/nfs4idmap.c
+++ b/fs/nfs/nfs4idmap.c
@@ -100,10 +100,12 @@ static bool nfs_fattr_map_owner_name(struct nfs_server *server, struct nfs_fattr
{
struct nfs4_string *owner = fattr->owner_name;
kuid_t uid;
+ int ret;

if (!(fattr->valid & NFS_ATTR_FATTR_OWNER_NAME))
return false;
- if (nfs_map_name_to_uid(server, owner->data, owner->len, &uid) == 0) {
+ ret = nfs_map_name_to_uid(server, owner->data, owner->len, &uid);
+ if (ret == 0 || ret == -ENOENT) {
fattr->uid = uid;
fattr->valid |= NFS_ATTR_FATTR_OWNER;
}
@@ -114,10 +116,12 @@ static bool nfs_fattr_map_group_name(struct nfs_server *server, struct nfs_fattr
{
struct nfs4_string *group = fattr->group_name;
kgid_t gid;
+ int ret;

if (!(fattr->valid & NFS_ATTR_FATTR_GROUP_NAME))
return false;
- if (nfs_map_group_to_gid(server, group->data, group->len, &gid) == 0) {
+ ret = nfs_map_group_to_gid(server, group->data, group->len, &gid);
+ if (ret == 0 || ret == -ENOENT) {
fattr->gid = gid;
fattr->valid |= NFS_ATTR_FATTR_GROUP;
}
@@ -351,20 +355,23 @@ static ssize_t nfs_idmap_lookup_name(__u32 id, const char *type, char *buf,
}

/* Name -> ID */
+/* Returns -ENOENT for unknown names (with @id set to the nobody id). */
static int nfs_idmap_lookup_id(const char *name, size_t namelen, const char *type,
__u32 *id, struct idmap *idmap)
{
- char id_str[NFS_UINT_MAXLEN];
+ char id_str[NFS_UINT_MAXLEN + 1];
long id_long;
ssize_t data_size;
int ret = 0;

- data_size = nfs_idmap_get_key(name, namelen, type, id_str, NFS_UINT_MAXLEN, idmap);
+ data_size = nfs_idmap_get_key(name, namelen, type, id_str, sizeof(id_str), idmap);
if (data_size <= 0) {
ret = -EINVAL;
} else {
ret = kstrtol(id_str, 10, &id_long);
*id = (__u32)id_long;
+ if (!ret && *id_str != '+')
+ ret = -ENOENT;
}
return ret;
}
@@ -719,9 +726,24 @@ int nfs_map_name_to_uid(const struct nfs_server *server, const char *name, size_
__u32 id = -1;
int ret = 0;

- if (!nfs_map_string_to_numeric(name, namelen, &id))
- ret = nfs_idmap_lookup_id(name, namelen, "uid", &id, idmap);
- if (ret == 0) {
+ if (!nfs_map_string_to_numeric(name, namelen, &id)) {
+ struct nfs_client *client = server->nfs_client;
+ const char *type;
+
+ for(;;) {
+ type = "xuid";
+ if (test_bit(NFS_CS_NOXUID, &client->cl_flags))
+ type = "uid";
+
+ ret = nfs_idmap_lookup_id(name, namelen, type, &id, idmap);
+ if (ret != -EINVAL || test_bit(NFS_CS_NOXUID, &client->cl_flags))
+ break;
+ printk(KERN_NOTICE "NFS: Falling back from nfsidmap "
+ "xuid/xgid to uid/gid\n");
+ set_bit(NFS_CS_NOXUID, &client->cl_flags);
+ }
+ }
+ if (ret == 0 || ret == -ENOENT) {
*uid = make_kuid(&init_user_ns, id);
if (!uid_valid(*uid))
ret = -ERANGE;
@@ -736,9 +758,24 @@ int nfs_map_group_to_gid(const struct nfs_server *server, const char *name, size
__u32 id = -1;
int ret = 0;

- if (!nfs_map_string_to_numeric(name, namelen, &id))
- ret = nfs_idmap_lookup_id(name, namelen, "gid", &id, idmap);
- if (ret == 0) {
+ if (!nfs_map_string_to_numeric(name, namelen, &id)) {
+ struct nfs_client *client = server->nfs_client;
+ const char *type;
+
+ for(;;) {
+ type = "xgid";
+ if (test_bit(NFS_CS_NOXUID, &client->cl_flags))
+ type = "gid";
+
+ ret = nfs_idmap_lookup_id(name, namelen, type, &id, idmap);
+ if (ret != -EINVAL || test_bit(NFS_CS_NOXUID, &client->cl_flags))
+ break;
+ printk(KERN_NOTICE "NFS: Falling back from nfsidmap "
+ "xuid/xgid to uid/gid\n");
+ set_bit(NFS_CS_NOXUID, &client->cl_flags);
+ }
+ }
+ if (ret == 0 || ret == -ENOENT) {
*gid = make_kgid(&init_user_ns, id);
if (!gid_valid(*gid))
ret = -ERANGE;
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index eefed15..adeb894 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -3875,7 +3875,8 @@ static int decode_attr_owner(struct xdr_stream *xdr, uint32_t *bitmap,
ret = NFS_ATTR_FATTR_OWNER_NAME;
}
} else if (len < XDR_MAX_NETOBJ) {
- if (nfs_map_name_to_uid(server, (char *)p, len, uid) == 0)
+ ret = nfs_map_name_to_uid(server, (char *)p, len, uid);
+ if (ret == 0 || ret == -ENOENT)
ret = NFS_ATTR_FATTR_OWNER;
else
dprintk("%s: nfs_map_name_to_uid failed!\n",
@@ -3918,7 +3919,8 @@ static int decode_attr_group(struct xdr_stream *xdr, uint32_t *bitmap,
ret = NFS_ATTR_FATTR_GROUP_NAME;
}
} else if (len < XDR_MAX_NETOBJ) {
- if (nfs_map_group_to_gid(server, (char *)p, len, gid) == 0)
+ ret = nfs_map_group_to_gid(server, (char *)p, len, gid);
+ if (ret == 0 || ret == -ENOENT)
ret = NFS_ATTR_FATTR_GROUP;
else
dprintk("%s: nfs_map_group_to_gid failed!\n",
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 570a7df..c7d42b7 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -36,6 +36,7 @@ struct nfs_client {
#define NFS_CS_RENEWD 3 /* - renewd started */
#define NFS_CS_STOP_RENEW 4 /* no more state to renew */
#define NFS_CS_CHECK_LEASE_TIME 5 /* need to check lease time */
+#define NFS_CS_NOXUID 6 /* don't use idmap xuid / xgid */
unsigned long cl_flags; /* behavior switches */
#define NFS_CS_NORESVPORT 0 /* - use ephemeral src port */
#define NFS_CS_DISCRTRY 1 /* - disconnect on RPC retry */