[PATCH 3/4] smb: client: fix potential UAF in smb2_is_valid_lease_break()

[Chanho Min <chanho.min@lge.com>]

From: Paulo Alcantara <pc@manguebit.com>

Skip sessions that are being teared down (status == SES_EXITING) to
avoid UAF.

Cc: stable@vger.kernel.org # 5.4
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
[ chanho: Backported to v5.4.y, smb2misc.c was moved from fs/cifs to fs/smb/client ]
Signed-off-by: Chanho Min <chanho.min@lge.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/cifs/smb2misc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index d7cbf1b07126c..c47927d257635 100644
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -611,7 +611,8 @@ smb2_is_valid_lease_break(char *buffer)
 
 		list_for_each(tmp1, &server->smb_ses_list) {
 			ses = list_entry(tmp1, struct cifs_ses, smb_ses_list);
-
+			if (cifs_ses_exiting(ses))
+				continue;
 			list_for_each(tmp2, &ses->tcon_list) {
 				tcon = list_entry(tmp2, struct cifs_tcon,
 						  tcon_list);