From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Tue, 22 Jun 2021 13:59:55 +0300
Subject: [PATCH] cifs: fix NULL dereference in smb2_check_message()
Git-commit: 1689b0b554defd5a7863bbd434ae911b8869504a
References: bsc#1190317
Patch-mainline: v5.13

This code sets "ses" to NULL which will lead to a NULL dereference on
the second iteration through the loop.

[ ematsumiya: replace list_entry_is_head() with its definition to avoid extra backport ]

Fixes: 85346c17e425 ("cifs: convert list_for_each to entry variant in smb2misc.c")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
---
 fs/cifs/smb2misc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -169,11 +169,9 @@ smb2_check_message(char *buf, unsigned i
 		list_for_each_entry(ses, &srvr->smb_ses_list, smb_ses_list) {
 			if (ses->Suid == thdr->SessionId)
 				break;
-
-			ses = NULL;
 		}
 		spin_unlock(&cifs_tcp_ses_lock);
-		if (ses == NULL) {
+		if (&ses->smb_ses_list == &srvr->smb_ses_list) {
 			cifs_dbg(VFS, "no decryption - session id not found\n");
 			return 1;
 		}