From: Darrick J. Wong <djwong@xxxxxxxxxx> I noticed that callers of xfs_qm_vop_dqalloc use the following code to compute the anticipated uid of the new file: mapped_fsuid(idmap, &init_user_ns); whereas the VFS uses a slightly different computation for actually assigning i_uid: mapped_fsuid(idmap, i_user_ns(inode)); Technically, these are not the same things. According to Christian Brauner, the only time that inode->i_sb->s_user_ns != &init_user_ns is when the filesystem was mounted in a new mount namespace by an unpriviledged user. XFS does not allow this, which is why we've never seen bug reports about quotas being incorrect or the uid checks in xfs_qm_vop_create_dqattach tripping debug assertions. However, this /is/ a logic bomb, so let's make the code consistent. Link: https://lore.kernel.org/linux-fsdevel/20240617-weitblick-gefertigt-4a41f37119fa@brauner/ Fixes: c14329d39f2d ("fs: port fs{g,u}id helpers to mnt_idmap") Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> --- fs/xfs/xfs_inode.c | 16 ++++++++++------ fs/xfs/xfs_symlink.c | 8 +++++--- 2 files changed, 15 insertions(+), 9 deletions(-) diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index aa134687027ca..5039509785090 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -1059,10 +1059,12 @@ xfs_create( prid = xfs_get_initial_prid(dp); /* - * Make sure that we have allocated dquot(s) on disk. + * Make sure that we have allocated dquot(s) on disk. The uid/gid + * computation code must match what the VFS uses to assign i_[ug]id. + * INHERIT adjusts the gid computation for setgid/grpid systems. */ - error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, &init_user_ns), - mapped_fsgid(idmap, &init_user_ns), prid, + error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, i_user_ns(VFS_I(dp))), + mapped_fsgid(idmap, i_user_ns(VFS_I(dp))), prid, XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT, &udqp, &gdqp, &pdqp); if (error) @@ -1234,10 +1236,12 @@ xfs_create_tmpfile( prid = xfs_get_initial_prid(dp); /* - * Make sure that we have allocated dquot(s) on disk. + * Make sure that we have allocated dquot(s) on disk. The uid/gid + * computation code must match what the VFS uses to assign i_[ug]id. + * INHERIT adjusts the gid computation for setgid/grpid systems. */ - error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, &init_user_ns), - mapped_fsgid(idmap, &init_user_ns), prid, + error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, i_user_ns(VFS_I(dp))), + mapped_fsgid(idmap, i_user_ns(VFS_I(dp))), prid, XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT, &udqp, &gdqp, &pdqp); if (error) diff --git a/fs/xfs/xfs_symlink.c b/fs/xfs/xfs_symlink.c index 17aee806ec2e1..53ed512c6f211 100644 --- a/fs/xfs/xfs_symlink.c +++ b/fs/xfs/xfs_symlink.c @@ -122,10 +122,12 @@ xfs_symlink( prid = xfs_get_initial_prid(dp); /* - * Make sure that we have allocated dquot(s) on disk. + * Make sure that we have allocated dquot(s) on disk. The uid/gid + * computation code must match what the VFS uses to assign i_[ug]id. + * INHERIT adjusts the gid computation for setgid/grpid systems. */ - error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, &init_user_ns), - mapped_fsgid(idmap, &init_user_ns), prid, + error = xfs_qm_vop_dqalloc(dp, mapped_fsuid(idmap, i_user_ns(VFS_I(dp))), + mapped_fsgid(idmap, i_user_ns(VFS_I(dp))), prid, XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT, &udqp, &gdqp, &pdqp); if (error)
