[PATCH] statx: don't leak STATX_ATTR_CHANGE_MONOTONIC in stx_attributes_mask

[PATCH] statx: don't leak STATX_ATTR_CHANGE_MONOTONIC in stx_attributes_mask

[Jeff Layton]

STATX_ATTR_CHANGE_MONOTONIC is kernel-internal. cp_statx() strips it
from stx_attributes but copies attributes_mask verbatim, so it leaks to
userland on filesystems that advertise it (nfs, ceph), e.g.
stx_attributes_mask = 0x8000000000b03000 on NFS.

Mask it out of stx_attributes_mask too.

Fixes: a1175d6b1bda ("vfs: plumb i_version handling into struct kstat")
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/stat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/stat.c b/fs/stat.c
index a2e63c6c45b7..787c13f378ff 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -719,7 +719,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
 	tmp.stx_ino = stat->ino;
 	tmp.stx_size = stat->size;
 	tmp.stx_blocks = stat->blocks;
-	tmp.stx_attributes_mask = stat->attributes_mask;
+	tmp.stx_attributes_mask = stat->attributes_mask & ~STATX_ATTR_CHANGE_MONOTONIC;
 	tmp.stx_atime.tv_sec = stat->atime.tv_sec;
 	tmp.stx_atime.tv_nsec = stat->atime.tv_nsec;
 	tmp.stx_btime.tv_sec = stat->btime.tv_sec;

---
base-commit: c339f4010dea8b0d754f84ace70cd1b089878ef8
change-id: 20261029-statx-3f1d8cd8d877

Best regards,
-- 
Jeff Layton <jlayton@kernel.org>