* [PATCH 7/8] vfs: Allow filesystems with foreign owner IDs to override UID checks
[not found] <20260727130827.1100080-1-dhowells@redhat.com>
@ 2026-07-27 13:08 ` David Howells
2026-07-28 7:43 ` Christian Brauner
0 siblings, 1 reply; 2+ messages in thread
From: David Howells @ 2026-07-27 13:08 UTC (permalink / raw)
To: Christian Brauner
Cc: David Howells, Marc Dionne, linux-afs, linux-fsdevel,
linux-kernel, Etienne Champetier, Jeffrey Altman, Chet Ramey,
Cheyenne Wills, Alexander Viro, Christian Brauner, Steve French,
Mimi Zohar, openafs-devel, linux-cifs, linux-integrity
A number of ownership checks made by the VFS make a number of assumptions:
(1) that it is meaningful to compare inode->i_uid to a second ->i_uid or
to current_fsuid(),
(2) that current_fsuid() represents the subject of the action,
(3) that the number in ->i_uid belong to the system's ID space and
(4) that the IDs can be represented by 32-bit integers.
Network filesystems, however, may violate all four of these assumptions.
Indeed, a network filesystem may not even have an actual concept of a UNIX
integer UID (cifs without POSIX extensions, for example). Plug-in block
filesystems (e.g. USB drives) may also violate this assumption.
In particular, AFS implements its own ACL security model with its own
per-cell user ID space with 64-bit IDs for some server variants. The
subject is represented by a token in a key, not current_fsuid(). The AFS
user IDs and the system user IDs for a cell may be numerically equivalent,
but that's matter of administrative policy and should perhaps be noted in
the cell definition or by mount option. A subsequent patch will address
AFS.
To help fix this, three functions are defined to perform UID comparison
within the VFS:
(1) vfs_inode_is_owned_by_me(). This defaults to comparing i_uid to
current_fsuid(), with appropriate namespace mapping, assuming that the
fsuid identifies the subject of the action. The filesystem may
override it by implementing an inode op:
int (*is_owned_by_me)(struct mnt_idmap *idmap, struct inode *inode);
This should return 0 if owned, 1 if not or an error if there's some
sort of lookup failure. It may use a means of identifying the subject
of the action other than fsuid, for example by using an authentication
token stored in a key.
(2) vfs_inodes_have_same_owner(). This defaults to comparing the i_uids
of two different inodes with appropriate namespace mapping. The
filesystem may override it by implementing another inode op:
int (*have_same_owner)(struct mnt_idmap *idmap, struct inode *inode1,
struct inode *inode2);
Again, this should return 0 if matching, 1 if not or an error if
there's some sort of lookup failure.
(3) vfs_inode_and_dir_have_same_owner(). This is similar to (2), but
assumes that the second inode is the parent directory to the first and
takes a nameidata struct instead of a second inode pointer.
In addition IOP_OWNERSHIP_OVERRIDE is added to i_opflags to control access
to these new inode ops.
Fix a number of places within the VFS where such UID checks are made that
should be deferring interpretation to the filesystem.
(*) chown_ok()
(*) chgrp_ok()
Call vfs_inode_is_owned_by_me(). Possibly these need to defer all
their checks to the network filesystem as the interpretation of the
new UID/GID depends on the netfs too, but the ->setattr() method gets
a chance to deal with that.
(*) coredump_file()
Call vfs_is_owned_by_me() to check that the file created is owned by
the caller - but the check that's there might be sufficient.
(*) inode_owner_or_capable()
Call vfs_is_owned_by_me(). I'm not sure whether the namespace mapping
makes sense in such a case, but it probably could be used.
(*) vfs_setlease()
Call vfs_is_owned_by_me(). Actually, it should query if leasing is
permitted.
Also, setting locks could perhaps do with a permission call to the
filesystem driver as AFS, for example, has a lock permission bit in
the ACL, but since the AFS server checks that when the RPC call is
made, it's probably unnecessary.
(*) acl_permission_check()
(*) posix_acl_permission()
Unchanged. These functions are only used by generic_permission()
which is overridden if ->permission() is supplied, and when evaluating
a POSIX ACL, it should arguably be checking the UID anyway.
AFS, for example, implements its own ACLs and evaluates them in
->permission() and on the server.
(*) may_follow_link()
Call vfs_inode_and_dir_have_same_owner() and vfs_is_owned_by_me() on
the the link and its parent dir.
(*) may_create_in_sticky()
Call vfs_is_owned_by_me() and also vfs_inode_and_dir_have_same_owner()
both.
[?] Should this return ok immediately if the open call we're in
created the file being checked.
(*) __check_sticky()
Call vfs_is_owned_by_me() on both the dir and the inode, but for AFS
vfs_is_owned_by_me() on a directory doesn't work, so call
vfs_inodes_have_same_owner() instead to check the directory (as is
done in may_create_in_sticky()).
(*) may_dedupe_file()
Call vfs_is_owned_by_me().
(*) IMA policy ops.
Unchanged for now. I'm not sure what the best way to deal with this
is - if, indeed, it needs any changes.
Note that wrapping stuff up into vfs_inode_is_owned_by_me() isn't
necessarily the most efficient as it means we may end up doing the uid
idmapping an extra time - though this is only done in three places, all to
do with world-writable sticky dir checks.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Etienne Champetier <champetier.etienne@gmail.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Chet Ramey <chet.ramey@case.edu>
cc: Cheyenne Wills <cwills@sinenomine.net>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Christian Brauner <brauner@kernel.org>
cc: Steve French <sfrench@samba.org>
cc: Mimi Zohar <zohar@linux.ibm.com>
cc: linux-afs@lists.infradead.org
cc: openafs-devel@openafs.org
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-integrity@vger.kernel.org
Link: https://groups.google.com/g/gnu.bash.bug/c/6PPTfOgFdL4/m/2AQU-S1N76UJ
Link: https://git.savannah.gnu.org/cgit/bash.git/tree/redir.c?h=bash-5.3-rc1#n733
---
Documentation/filesystems/vfs.rst | 21 ++++
fs/attr.c | 58 ++++++-----
fs/coredump.c | 2 +-
fs/inode.c | 11 +-
fs/internal.h | 1 +
fs/locks.c | 7 +-
fs/namei.c | 161 ++++++++++++++++++++++++------
fs/remap_range.c | 20 ++--
include/linux/fs.h | 7 +-
9 files changed, 217 insertions(+), 71 deletions(-)
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 7c753148af88..893419e003ea 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -445,6 +445,9 @@ As of kernel 2.6.22, the following members are defined:
struct dentry *dentry, struct file_kattr *fa);
int (*fileattr_get)(struct dentry *dentry, struct file_kattr *fa);
struct offset_ctx *(*get_offset_ctx)(struct inode *inode);
+ int (*is_owned_by_me)(struct mnt_idmap *idmap, struct inode *inode);
+ int (*have_same_owner)(struct mnt_idmap *idmap, struct inode *inode,
+ struct dentry *dentry);
};
Again, all methods are called without any locks being held, unless
@@ -634,6 +637,24 @@ otherwise noted.
filesystem must define this operation to use
simple_offset_dir_operations.
+``is_owned_by_me``
+ called to determine if the file can be considered to be 'owned' by
+ the owner of the process or if the process has a token that grants
+ it ownership privileges. If unset, the default is to compare i_uid
+ to current_fsuid() - but this may give incorrect results for some
+ network or plug-in block filesystems. For example, AFS determines
+ ownership entirely according to an obtained token and i_uid may not
+ even be from the same ID space as current_uid().
+
+``have_same_owner``
+ called to determine if an inode has the same owner as its immediate
+ parent on the path walked. If unset, the default is to simply
+ compare the i_uid of both. For example, AFS compares the owner IDs
+ of both - but these are a 64-bit values on some variants that might
+ not fit into a kuid_t and cifs has GUIDs that cannot be compared to
+ kuid_t.
+
+
The Address Space Object
========================
diff --git a/fs/attr.c b/fs/attr.c
index 4f437fabb7f0..b7e8b5d49a9f 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -16,6 +16,7 @@
#include <linux/fcntl.h>
#include <linux/filelock.h>
#include <linux/security.h>
+#include "internal.h"
/**
* setattr_should_drop_sgid - determine whether the setgid bit needs to be
@@ -91,19 +92,21 @@ EXPORT_SYMBOL(setattr_should_drop_suidgid);
* permissions. On non-idmapped mounts or if permission checking is to be
* performed on the raw inode simply pass @nop_mnt_idmap.
*/
-static bool chown_ok(struct mnt_idmap *idmap,
- const struct inode *inode, vfsuid_t ia_vfsuid)
+static int chown_ok(struct mnt_idmap *idmap,
+ struct inode *inode, vfsuid_t ia_vfsuid)
{
vfsuid_t vfsuid = i_uid_into_vfsuid(idmap, inode);
- if (vfsuid_eq_kuid(vfsuid, current_fsuid()) &&
- vfsuid_eq(ia_vfsuid, vfsuid))
- return true;
+ int ret;
+
+ ret = vfs_inode_is_owned_by_me(idmap, inode);
+ if (ret <= 0)
+ return ret;
if (capable_wrt_inode_uidgid(idmap, inode, CAP_CHOWN))
- return true;
+ return 0;
if (!vfsuid_valid(vfsuid) &&
ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
- return true;
- return false;
+ return 0;
+ return -EPERM;
}
/**
@@ -118,23 +121,27 @@ static bool chown_ok(struct mnt_idmap *idmap,
* permissions. On non-idmapped mounts or if permission checking is to be
* performed on the raw inode simply pass @nop_mnt_idmap.
*/
-static bool chgrp_ok(struct mnt_idmap *idmap,
- const struct inode *inode, vfsgid_t ia_vfsgid)
+static int chgrp_ok(struct mnt_idmap *idmap,
+ struct inode *inode, vfsgid_t ia_vfsgid)
{
vfsgid_t vfsgid = i_gid_into_vfsgid(idmap, inode);
- vfsuid_t vfsuid = i_uid_into_vfsuid(idmap, inode);
- if (vfsuid_eq_kuid(vfsuid, current_fsuid())) {
+ int ret;
+
+ ret = vfs_inode_is_owned_by_me(idmap, inode);
+ if (ret < 0)
+ return ret;
+ if (ret == 0) {
if (vfsgid_eq(ia_vfsgid, vfsgid))
- return true;
+ return 0;
if (vfsgid_in_group_p(ia_vfsgid))
- return true;
+ return 0;
}
if (capable_wrt_inode_uidgid(idmap, inode, CAP_CHOWN))
- return true;
+ return 0;
if (!vfsgid_valid(vfsgid) &&
ns_capable(inode->i_sb->s_user_ns, CAP_CHOWN))
- return true;
- return false;
+ return 0;
+ return -EPERM;
}
/**
@@ -163,6 +170,7 @@ int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
{
struct inode *inode = d_inode(dentry);
unsigned int ia_valid = attr->ia_valid;
+ int ret;
/*
* First check size constraints. These can't be overridden using
@@ -189,14 +197,18 @@ int setattr_prepare(struct mnt_idmap *idmap, struct dentry *dentry,
goto kill_priv;
/* Make sure a caller can chown. */
- if ((ia_valid & ATTR_UID) &&
- !chown_ok(idmap, inode, attr->ia_vfsuid))
- return -EPERM;
+ if (ia_valid & ATTR_UID) {
+ ret = chown_ok(idmap, inode, attr->ia_vfsuid);
+ if (ret < 0)
+ return ret;
+ }
/* Make sure caller can chgrp. */
- if ((ia_valid & ATTR_GID) &&
- !chgrp_ok(idmap, inode, attr->ia_vfsgid))
- return -EPERM;
+ if (ia_valid & ATTR_GID) {
+ ret = chgrp_ok(idmap, inode, attr->ia_vfsgid);
+ if (ret < 0)
+ return ret;
+ }
/* Make sure a caller can chmod. */
if (ia_valid & ATTR_MODE) {
diff --git a/fs/coredump.c b/fs/coredump.c
index e68a76ff92a3..3f32e73aaeda 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -954,7 +954,7 @@ static bool coredump_file(struct core_name *cn, struct coredump_params *cprm,
* filesystem.
*/
idmap = file_mnt_idmap(file);
- if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid())) {
+ if (vfs_inode_is_owned_by_me(idmap, inode) != 0) {
coredump_report_failure("Core dump to %s aborted: cannot preserve file owner", cn->corename);
return false;
}
diff --git a/fs/inode.c b/fs/inode.c
index 31c5b9ee3a81..a7ec830ab683 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2750,16 +2750,19 @@ EXPORT_SYMBOL(inode_init_owner);
* On non-idmapped mounts or if permission checking is to be performed on the
* raw inode simply pass @nop_mnt_idmap.
*/
-bool inode_owner_or_capable(struct mnt_idmap *idmap,
- const struct inode *inode)
+bool inode_owner_or_capable(struct mnt_idmap *idmap, struct inode *inode)
{
vfsuid_t vfsuid;
struct user_namespace *ns;
+ int ret;
- vfsuid = i_uid_into_vfsuid(idmap, inode);
- if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
+ ret = vfs_inode_is_owned_by_me(idmap, inode);
+ if (ret == 0)
return true;
+ if (ret < 0)
+ return false;
+ vfsuid = i_uid_into_vfsuid(idmap, inode);
ns = current_user_ns();
if (vfsuid_has_mapping(ns, vfsuid) && ns_capable(ns, CAP_FOWNER))
return true;
diff --git a/fs/internal.h b/fs/internal.h
index 355d93f92208..be45cc638861 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -51,6 +51,7 @@ extern int finish_clean_context(struct fs_context *fc);
/*
* namei.c
*/
+int vfs_inode_is_owned_by_me(struct mnt_idmap *idmap, struct inode *inode);
extern int filename_lookup(int dfd, struct filename *name, unsigned flags,
struct path *path, const struct path *root);
int filename_rmdir(int dfd, struct filename *name);
diff --git a/fs/locks.c b/fs/locks.c
index 6e4ff7fcec05..02f810dc9e7e 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -68,6 +68,7 @@
#include <trace/events/filelock.h>
#include <linux/uaccess.h>
+#include "internal.h"
static struct file_lock *file_lock(struct file_lock_core *flc)
{
@@ -2136,10 +2137,12 @@ int
vfs_setlease(struct file *filp, int arg, struct file_lease **lease, void **priv)
{
struct inode *inode = file_inode(filp);
- vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_idmap(filp), inode);
int error;
- if ((!vfsuid_eq_kuid(vfsuid, current_fsuid())) && !capable(CAP_LEASE))
+ error = vfs_inode_is_owned_by_me(file_mnt_idmap(filp), inode);
+ if (error < 0)
+ return error;
+ if (error != 0 && !capable(CAP_LEASE))
return -EACCES;
error = security_file_lock(filp, arg);
if (error)
diff --git a/fs/namei.c b/fs/namei.c
index 19ce43c9a6e6..72f94d204f93 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -55,8 +55,8 @@
* The new code replaces the old recursive symlink resolution with
* an iterative one (in case of non-nested symlink chains). It does
* this with calls to <fs>_follow_link().
- * As a side effect, dir_namei(), _namei() and follow_link() are now
- * replaced with a single function lookup_dentry() that can handle all
+ * As a side effect, dir_namei(), _namei() and follow_link() are now
+ * replaced with a single function lookup_dentry() that can handle all
* the special cases of the former code.
*
* With the new dcache, the pathname is stored at each inode, at least as
@@ -1255,6 +1255,72 @@ fs_initcall(init_fs_namei_sysctls);
#endif /* CONFIG_SYSCTL */
+/*
+ * Determine if an inode is owned by the process (allowing for fsuid override),
+ * returning 0 if so, 1 if not and a negative error code if there was a problem
+ * making the determination.
+ */
+int vfs_inode_is_owned_by_me(struct mnt_idmap *idmap, struct inode *inode)
+{
+ if (unlikely(inode->i_opflags & IOP_OWNERSHIP_OVERRIDE))
+ return inode->i_op->is_owned_by_me(idmap, inode);
+ if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid()))
+ return 0;
+ return 1; /* Not same. */
+}
+
+/*
+ * Determine if an inode has the same owner as its parent directory, returning
+ * 0 if so, 1 if not and a negative error code if there was a problem making
+ * the determination.
+ */
+static int vfs_inode_and_dir_have_same_owner(struct mnt_idmap *idmap, struct inode *inode,
+ const struct nameidata *nd)
+{
+ if (unlikely(inode->i_opflags & IOP_OWNERSHIP_OVERRIDE)) {
+ struct dentry *parent;
+ struct inode *dir;
+ int ret;
+
+ if (inode != nd->inode) {
+ dir = nd->inode;
+ ret = inode->i_op->have_same_owner(idmap, inode, dir);
+ } else if (nd->flags & LOOKUP_RCU) {
+ parent = READ_ONCE(nd->path.dentry);
+ dir = READ_ONCE(parent->d_inode);
+ if (!dir)
+ return -ECHILD;
+ ret = inode->i_op->have_same_owner(idmap, inode, dir);
+ } else {
+ parent = dget_parent(nd->path.dentry);
+ dir = parent->d_inode;
+ ret = inode->i_op->have_same_owner(idmap, inode, dir);
+ dput(parent);
+ }
+ return ret;
+ }
+
+ if (vfsuid_valid(nd->dir_vfsuid) &&
+ vfsuid_eq(i_uid_into_vfsuid(idmap, inode), nd->dir_vfsuid))
+ return 0;
+ return 1; /* Not same. */
+}
+
+/*
+ * Determine if two inodes have the same owner, returning 0 if so, 1 if not and
+ * a negative error code if there was a problem making the determination.
+ */
+static int vfs_inodes_have_same_owner(struct mnt_idmap *idmap, struct inode *inode,
+ struct inode *dir)
+{
+ if (unlikely(inode->i_opflags & IOP_OWNERSHIP_OVERRIDE))
+ return inode->i_op->have_same_owner(idmap, inode, dir);
+ if (vfsuid_eq(i_uid_into_vfsuid(idmap, inode),
+ i_uid_into_vfsuid(idmap, dir)))
+ return 0;
+ return 1; /* Not same. */
+}
+
/**
* may_follow_link - Check symlink following for unsafe situations
* @nd: nameidata pathwalk data
@@ -1271,27 +1337,28 @@ fs_initcall(init_fs_namei_sysctls);
*
* Returns 0 if following the symlink is allowed, -ve on error.
*/
-static inline int may_follow_link(struct nameidata *nd, const struct inode *inode)
+static inline int may_follow_link(struct nameidata *nd, struct inode *inode)
{
struct mnt_idmap *idmap;
- vfsuid_t vfsuid;
+ int ret;
if (!sysctl_protected_symlinks)
return 0;
- idmap = mnt_idmap(nd->path.mnt);
- vfsuid = i_uid_into_vfsuid(idmap, inode);
- /* Allowed if owner and follower match. */
- if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
- return 0;
-
/* Allowed if parent directory not sticky and world-writable. */
if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
return 0;
+ idmap = mnt_idmap(nd->path.mnt);
+ /* Allowed if owner and follower match. */
+ ret = vfs_inode_is_owned_by_me(idmap, inode);
+ if (ret <= 0)
+ return ret;
+
/* Allowed if parent directory and link owner match. */
- if (vfsuid_valid(nd->dir_vfsuid) && vfsuid_eq(nd->dir_vfsuid, vfsuid))
- return 0;
+ ret = vfs_inode_and_dir_have_same_owner(idmap, inode, nd);
+ if (ret <= 0)
+ return ret;
if (nd->flags & LOOKUP_RCU)
return -ECHILD;
@@ -1389,12 +1456,12 @@ int may_linkat(struct mnt_idmap *idmap, const struct path *link)
* @inode: the inode of the file to open
*
* Block an O_CREAT open of a FIFO (or a regular file) when:
- * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
- * - the file already exists
- * - we are in a sticky directory
- * - we don't own the file
+ * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled,
+ * - the file already exists,
+ * - we are in a sticky directory,
+ * - the directory is world writable,
+ * - we don't own the file and
* - the owner of the directory doesn't own the file
- * - the directory is world writable
* If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
* the directory doesn't have to be world writable: being group writable will
* be enough.
@@ -1405,13 +1472,45 @@ int may_linkat(struct mnt_idmap *idmap, const struct path *link)
* On non-idmapped mounts or if permission checking is to be performed on the
* raw inode simply pass @nop_mnt_idmap.
*
+ * For a filesystem (e.g. a network filesystem) that has a separate ID space
+ * and has foreign IDs (maybe even non-integer IDs), i_uid cannot be compared
+ * to current_fsuid() and may not be directly comparable to another i_uid.
+ * Instead, the filesystem is asked to perform the comparisons. With network
+ * filesystems, there also exists the possibility of doing anonymous
+ * operations and having anonymously-owned objects.
+ *
+ * We have the following scenarios:
+ *
+ * USER DIR FILE FILE ALLOWED
+ * OWNER OWNER STATE
+ * ======= ======= ======= ======= =======
+ * A A - New Yes
+ * A A A Exists Yes
+ * A A C Exists No
+ * A B - New Yes
+ * A B A Exists Yes, FO==U
+ * A B B Exists Yes, FO==DO
+ * A B C Exists No
+ * A anon[1] - New Yes
+ * A anon[1] A Exists Yes
+ * A anon[1] C Exists No
+ * anon A - New Yes
+ * anon A A Exists Yes, FO==DO
+ * anon anon[1] - New Yes
+ * anon anon[1] - Exists No
+ * anon A A Exists Yes, FO==DO
+ * anon A C Exists No
+ * anon A anon Exists No
+ *
+ * [1] Can anonymously-owned dirs be sticky?
+ *
* Returns 0 if the open is allowed, -ve on error.
*/
static int may_create_in_sticky(struct mnt_idmap *idmap, struct nameidata *nd,
- struct inode *const inode)
+ struct inode *inode)
{
umode_t dir_mode = nd->dir_mode;
- vfsuid_t dir_vfsuid = nd->dir_vfsuid, i_vfsuid;
+ int ret;
if (likely(!(dir_mode & S_ISVTX)))
return 0;
@@ -1422,13 +1521,13 @@ static int may_create_in_sticky(struct mnt_idmap *idmap, struct nameidata *nd,
if (S_ISFIFO(inode->i_mode) && !sysctl_protected_fifos)
return 0;
- i_vfsuid = i_uid_into_vfsuid(idmap, inode);
-
- if (vfsuid_eq(i_vfsuid, dir_vfsuid))
- return 0;
+ ret = vfs_inode_and_dir_have_same_owner(idmap, inode, nd);
+ if (ret <= 0)
+ return ret;
- if (vfsuid_eq_kuid(i_vfsuid, current_fsuid()))
- return 0;
+ ret = vfs_inode_is_owned_by_me(idmap, inode);
+ if (ret <= 0)
+ return ret;
if (likely(dir_mode & 0002)) {
audit_log_path_denied(AUDIT_ANOM_CREAT, "sticky_create");
@@ -3645,12 +3744,14 @@ EXPORT_SYMBOL(user_path_at);
int __check_sticky(struct mnt_idmap *idmap, struct inode *dir,
struct inode *inode)
{
- kuid_t fsuid = current_fsuid();
+ int ret;
- if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), fsuid))
- return 0;
- if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, dir), fsuid))
- return 0;
+ ret = vfs_inode_is_owned_by_me(idmap, inode);
+ if (ret <= 0)
+ return ret;
+ ret = vfs_inodes_have_same_owner(idmap, inode, dir);
+ if (ret <= 0)
+ return ret;
return !capable_wrt_inode_uidgid(idmap, inode, CAP_FOWNER);
}
EXPORT_SYMBOL(__check_sticky);
diff --git a/fs/remap_range.c b/fs/remap_range.c
index 26afbbbfb10c..9eee93c27001 100644
--- a/fs/remap_range.c
+++ b/fs/remap_range.c
@@ -413,20 +413,22 @@ loff_t vfs_clone_file_range(struct file *file_in, loff_t pos_in,
EXPORT_SYMBOL(vfs_clone_file_range);
/* Check whether we are allowed to dedupe the destination file */
-static bool may_dedupe_file(struct file *file)
+static int may_dedupe_file(struct file *file)
{
struct mnt_idmap *idmap = file_mnt_idmap(file);
struct inode *inode = file_inode(file);
+ int ret;
if (capable(CAP_SYS_ADMIN))
- return true;
+ return 0;
if (file->f_mode & FMODE_WRITE)
- return true;
- if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid()))
- return true;
+ return 0;
+ ret = vfs_inode_is_owned_by_me(idmap, inode);
+ if (ret <= 0)
+ return ret;
if (!inode_permission(idmap, inode, MAY_WRITE))
- return true;
- return false;
+ return 0;
+ return -EPERM;
}
loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
@@ -459,8 +461,8 @@ loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
if (ret)
return ret;
- ret = -EPERM;
- if (!may_dedupe_file(dst_file))
+ ret = may_dedupe_file(dst_file);
+ if (ret < 0)
goto out_drop_write;
ret = -EXDEV;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 50ce731a2b78..8013c13a353d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -628,6 +628,7 @@ is_uncached_acl(struct posix_acl *acl)
#define IOP_CACHED_LINK 0x0040
#define IOP_FASTPERM_MAY_EXEC 0x0080
#define IOP_FLCTX 0x0100
+#define IOP_OWNERSHIP_OVERRIDE 0x0200 /* Use ->is_owned_by_me() and ->have_same_owner() */
/*
* Inode state bits. Protected by inode->i_lock
@@ -1755,8 +1756,7 @@ static inline bool file_write_not_started(const struct file *file)
return sb_write_not_started(file_inode(file)->i_sb);
}
-bool inode_owner_or_capable(struct mnt_idmap *idmap,
- const struct inode *inode);
+bool inode_owner_or_capable(struct mnt_idmap *idmap, struct inode *inode);
/*
* VFS helper functions..
@@ -2036,6 +2036,9 @@ struct inode_operations {
struct dentry *dentry, struct file_kattr *fa);
int (*fileattr_get)(struct dentry *dentry, struct file_kattr *fa);
struct offset_ctx *(*get_offset_ctx)(struct inode *inode);
+ int (*is_owned_by_me)(struct mnt_idmap *idmap, struct inode *inode);
+ int (*have_same_owner)(struct mnt_idmap *idmap, struct inode *inode1,
+ struct inode *inode2);
} ____cacheline_aligned;
/* Did the driver provide valid mmap hook configuration? */
^ permalink raw reply related [flat|nested] 2+ messages in thread