From f38152ecf9087ef5f8df01c3bc65e57f4d597198 Mon Sep 17 00:00:00 2001 From: Michael Bommarito Date: Mon, 20 Apr 2026 21:50:58 +0800 Subject: [PATCH] smb: client: require a full NFS mode SID before reading mode bits ANBZ: #34936 commit b53b8e98c23310294fc45fc686db5ee860311896 stable. commit 2757ad3e4b6f9e0fed4c7739594e702abc5cab21 upstream. parse_dacl() treats an ACE SID matching sid_unix_NFS_mode as an NFS mode SID and reads sid.sub_auth[2] to recover the mode bits. That assumes the ACE carries three subauthorities, but compare_sids() only compares min(a, b) subauthorities. A malicious server can return an ACE with num_subauth = 2 and sub_auth[] = {88, 3}, which still matches sid_unix_NFS_mode and then drives the sub_auth[2] read four bytes past the end of the ACE. Require num_subauth >= 3 before treating the ACE as an NFS mode SID. This keeps the fix local to the special-SID mode path without changing compare_sids() semantics for the rest of cifsacl. Fixes: e2f8fbfb8d09 ("cifs: get mode bits from special sid on stat") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Michael Bommarito Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman Fixes: CVE-2026-43350 Assisted-by: PatchPilot Signed-off-by: Ferry Meng --- fs/smb/client/cifsacl.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c index 7bd29e827c8f..fb090e001e44 100644 --- a/fs/smb/client/cifsacl.c +++ b/fs/smb/client/cifsacl.c @@ -832,6 +832,7 @@ static void parse_dacl(struct smb_acl *pdacl, char *end_of_acl, dump_ace(ppace[i], end_of_acl); #endif if (mode_from_special_sid && + ppace[i]->sid.num_subauth >= 3 && (compare_sids(&(ppace[i]->sid), &sid_unix_NFS_mode) == 0)) { /* -- Gitee