[PATCH 2/4] smb: client: fix potential UAF in is_valid_oplock_break()

[Chanho Min]

From: Paulo Alcantara <pc@xxxxxxxxxxxxx>

commit 69ccf040acddf33a3a85ec0f6b45ef84b0f7ec29 upstream.

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

Cc: stable@xxxxxxxxxxxxxxx # 5.4
Signed-off-by: Paulo Alcantara (Red Hat) <pc@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
[ chanho: Backported to v5.4.y, misc.c was moved from fs/cifs to fs/smb/client ]
Signed-off-by: Chanho Min <chanho.min@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/cifs/misc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index db1fcdedf289a..4d838d7db7b57 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -473,6 +473,8 @@ is_valid_oplock_break(char *buffer, struct TCP_Server_Info *srv)
 	spin_lock(&cifs_tcp_ses_lock);
 	list_for_each(tmp, &srv->smb_ses_list) {
 		ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
+		if (cifs_ses_exiting(ses))
+			continue;
 		list_for_each(tmp1, &ses->tcon_list) {
 			tcon = list_entry(tmp1, struct cifs_tcon, tcon_list);
 			if (tcon->tid != buf->Tid)