smb: client: fix slab-out-of-bounds write in id_mode_to_cifs_acl()

In id_mode_to_cifs_acl(), while the chown branch reserves
sizeof(struct smb_ntsd) + 2 * sizeof(struct smb_sid) (plus
sizeof(struct smb_acl) and the worst-case ACE space after
commit 0ee150794c75 ("smb: client: fix heap overflow in DACL owner/group
rewrite")), the chmod branch only adds 2 * sizeof(struct smb_ace) or
5 * sizeof(struct smb_ace) to secdesclen (or 1 * sizeof(struct smb_ace)
on posix).

However, the chmod branch also invokes build_sec_desc() ->
copy_sec_desc(), which unconditionally writes the Owner SID at
pnntsd + sidsoffset and the Group SID at
pnntsd + sidsoffset + sizeof(struct smb_sid) (2 * 68 = 136 bytes total),
and set_chmod_dacl() always writes a struct smb_acl header (8 bytes)
even when the source descriptor has dacloffset == 0. When a security
descriptor has compact or overlapping Owner/Group SIDs (or
dacloffset == 0), calling chmod() under-allocates pnntsd and writes past
the end of the slab buffer.

Reserve sizeof(struct smb_acl) + 2 * sizeof(struct smb_sid) (plus
sizeof(struct smb_ntsd) on the posix path) in the chmod branch of
id_mode_to_cifs_acl().

Fixes: 7ee0b4c635c0 ("cifs: fix hardcoded default security descriptor length")
Fixes: f5065508897a ("cifs: Retain old ACEs when converting between mode bits and ACL.")
Assisted-by: ARTIST LLM
Signed-off-by: Dominik Maier <dmnk@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paulo Alcantara <pc@manguebit.org>

0 files changed, 0 insertions, 0 deletions