[PATCH] fs: reset read-only fsflags together with xflags

[Andrey Albershteyn]

While setting file attributes, the read-only flags are reset
for ->xflags, but not for ->flags if flag is shared between both. This
is fine for now as all read-only xflags don't overlap with flags.
However, for any read-only shared flag this will create inconsistency
between xflags and flags. The non-shared flag will be reset in
vfs_fileattr_set() to the current value, but shared one is past further
to ->fileattr_set.

Reported-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Andrey Albershteyn <aalbersh@xxxxxxxxxx>
---

The shared read-only flag is going to be added for fsverity. The one for ->flags
already exists.

[1]: https://lore.kernel.org/linux-xfs/20260119165644.2945008-2-aalbersh@xxxxxxxxxx/

---
 fs/file_attr.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/file_attr.c b/fs/file_attr.c
index 13cdb31a3e94..bed5442fa6fa 100644
--- a/fs/file_attr.c
+++ b/fs/file_attr.c
@@ -142,8 +142,7 @@ static int file_attr_to_fileattr(const struct file_attr *fattr,
 	if (fattr->fa_xflags & ~mask)
 		return -EINVAL;
 
-	fileattr_fill_xflags(fa, fattr->fa_xflags);
-	fa->fsx_xflags &= ~FS_XFLAG_RDONLY_MASK;
+	fileattr_fill_xflags(fa, fattr->fa_xflags & ~FS_XFLAG_RDONLY_MASK);
 	fa->fsx_extsize = fattr->fa_extsize;
 	fa->fsx_projid = fattr->fa_projid;
 	fa->fsx_cowextsize = fattr->fa_cowextsize;
@@ -163,8 +162,7 @@ static int copy_fsxattr_from_user(struct file_kattr *fa,
 	if (xfa.fsx_xflags & ~mask)
 		return -EOPNOTSUPP;
 
-	fileattr_fill_xflags(fa, xfa.fsx_xflags);
-	fa->fsx_xflags &= ~FS_XFLAG_RDONLY_MASK;
+	fileattr_fill_xflags(fa, xfa.fsx_xflags & ~FS_XFLAG_RDONLY_MASK);
 	fa->fsx_extsize = xfa.fsx_extsize;
 	fa->fsx_nextents = xfa.fsx_nextents;
 	fa->fsx_projid = xfa.fsx_projid;
-- 
2.52.0