[PATCH 5.10 CANDIDATE 11/11] xfs: use setattr_copy to set vfs inode attributes

Amir Goldstein
2022-06-17T10:07:45Z

From: "Darrick J. Wong" <djwong@kernel.org>

commit e014f37db1a2d109afa750042ac4d69cf3e3d88e upstream.

[remove userns argument of setattr_copy() for backport]

Filipe Manana pointed out that XFS' behavior w.r.t. setuid/setgid
revocation isn't consistent with btrfs[1] or ext4. Those two
filesystems use the VFS function setattr_copy to convey certain
attributes from struct iattr into the VFS inode structure.

Andrey Zhadchenko reported[2] that XFS uses the wrong user namespace to
decide if it should clear setgid and setuid on a file attribute update.
This is a second symptom of the problem that Filipe noticed.

XFS, on the other hand, open-codes setattr_copy in xfs_setattr_mode,
xfs_setattr_nonsize, and xfs_setattr_time. Regrettably, setattr_copy is
/not/ a simple copy function; it contains additional logic to clear the
setgid bit when setting the mode, and XFS' version no longer matches.

The VFS implements its own setuid/setgid stripping logic, which
establishes consistent behavior. It's a tad unfortunate that it's
scattered across notify_change, should_remove_suid, and setattr_copy but
XFS should really follow the Linux VFS. Adapt XFS to use the VFS
functions and get rid of the old functions.

[1] https://lore.kernel.org/fstests/CAL3q7H47iNQ=Wmk83WcGB-KBJVOEtR9+qGczzCeXJ9Y2KCV25Q@mail.gmail.com/
[2] https://lore.kernel.org/linux-xfs/20220221182218.748084-1-andrey.zhadchenko@virtuozzo.com/

Fixes: 7fa294c8991c ("userns: Allow chown and setgid preservation")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/xfs/xfs_iops.c | 56 +++--------------------------------------------
fs/xfs/xfs_pnfs.c | 3 ++-
2 files changed, 5 insertions(+), 54 deletions(-)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index b7f7b31a77d5..5711c8c12625 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -595,37 +595,6 @@ xfs_vn_getattr(
return 0;
}

-static void
-xfs_setattr_mode(
- struct xfs_inode *ip,
- struct iattr *iattr)
-{
- struct inode *inode = VFS_I(ip);
- umode_t mode = iattr->ia_mode;
-
- ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
-
- inode->i_mode &= S_IFMT;
- inode->i_mode |= mode & ~S_IFMT;
-}
-
-void
-xfs_setattr_time(
- struct xfs_inode *ip,
- struct iattr *iattr)
-{
- struct inode *inode = VFS_I(ip);
-
- ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
-
- if (iattr->ia_valid & ATTR_ATIME)
- inode->i_atime = iattr->ia_atime;
- if (iattr->ia_valid & ATTR_CTIME)
- inode->i_ctime = iattr->ia_ctime;
- if (iattr->ia_valid & ATTR_MTIME)
- inode->i_mtime = iattr->ia_mtime;
-}
-
static int
xfs_vn_change_ok(
struct dentry *dentry,
@@ -740,16 +709,6 @@ xfs_setattr_nonsize(
goto out_cancel;
}

- /*
- * CAP_FSETID overrides the following restrictions:
- *
- * The set-user-ID and set-group-ID bits of a file will be
- * cleared upon successful return from chown()
- */
- if ((inode->i_mode & (S_ISUID|S_ISGID)) &&
- !capable(CAP_FSETID))
- inode->i_mode &= ~(S_ISUID|S_ISGID);
-
/*
* Change the ownerships and register quota modifications
* in the transaction.
@@ -761,7 +720,6 @@ xfs_setattr_nonsize(
olddquot1 = xfs_qm_vop_chown(tp, ip,
&ip->i_udquot, udqp);
}
- inode->i_uid = uid;
}
if (!gid_eq(igid, gid)) {
if (XFS_IS_QUOTA_RUNNING(mp) && XFS_IS_GQUOTA_ON(mp)) {
@@ -772,15 +730,10 @@ xfs_setattr_nonsize(
olddquot2 = xfs_qm_vop_chown(tp, ip,
&ip->i_gdquot, gdqp);
}
- inode->i_gid = gid;
}
}

- if (mask & ATTR_MODE)
- xfs_setattr_mode(ip, iattr);
- if (mask & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME))
- xfs_setattr_time(ip, iattr);
-
+ setattr_copy(inode, iattr);
xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

XFS_STATS_INC(mp, xs_ig_attrchg);
@@ -1025,11 +978,8 @@ xfs_setattr_size(
xfs_inode_clear_eofblocks_tag(ip);
}

- if (iattr->ia_valid & ATTR_MODE)
- xfs_setattr_mode(ip, iattr);
- if (iattr->ia_valid & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME))
- xfs_setattr_time(ip, iattr);
-
+ ASSERT(!(iattr->ia_valid & (ATTR_UID | ATTR_GID)));
+ setattr_copy(inode, iattr);
xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

XFS_STATS_INC(mp, xs_ig_attrchg);
diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index f3082a957d5e..ae61094bc9d1 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -283,7 +283,8 @@ xfs_fs_commit_blocks(
xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

- xfs_setattr_time(ip, iattr);
+ ASSERT(!(iattr->ia_valid & (ATTR_UID | ATTR_GID)));
+ setattr_copy(inode, iattr);
if (update_isize) {
i_size_write(inode, iattr->ia_size);
ip->i_d.di_size = iattr->ia_size;
--
2.25.1