xfs: fix capability check in xfs

Browse source

An user reported a bug where he managed to evade group's quota
by changing a file's gid to a different group id the same user
belonged to, even though quotas were enforced on both gids and the
file's size was big enough to exceed the quota's hardlimit.

Commit eba0549bc7 replaced a capable() call by a
has_capability_noaudit() to prevent unnecessary selinux audit messages.
Turns out that both calls have slightly different semantics even though
their documentation seems similar. Where in a nutshell:

capable() - Tests the task's effective credentials
has_ns_capability_noaudit() - Tests the task's real credentials

This most of the time has no practical difference but in some cases like
changing attrs (specifically group id in this case) through a NFS client
this will allow the quota code to use XFS_QMOPT_FORCE_RES, effectively
bypassing quota accounting checks.

Using instead ns_capable_noaudit() should fix this issue and prevent
selinux audit messages.

This also fix the remaining calls to has_capability_noaudit()

Fixes: eba0549bc7 ("xfs: don't generate selinux audit messages for capability testing")
Cc: stable@vger.kernel.org # v5.18
Reported-by: Dr. Thomas Orgis <thomas.orgis@uni-hamburg.de>
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Serge Hallyn <sergeh@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

...

This commit is contained in:

Carlos Maiolino 2026-08-04 11:45:51 +02:00

parent 885435535b

commit e2f62a9744

3 changed files with 3 additions and 3 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

2

fs/xfs/xfs_fsmap.c

View file

2

fs/xfs/xfs_ioctl.c

View file

2

fs/xfs/xfs_iops.c

View file