[PATCH 5.15.y] smb: client: fix potential UAF in is_valid_oplock_break()

[Cliff Liu]

From: Paulo Alcantara <pc@xxxxxxxxxxxxx>

[ Upstream commit 69ccf040acddf33a3a85ec0f6b45ef84b0f7ec29 ]

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

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paulo Alcantara (Red Hat) <pc@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
[Minor context change fixed]
Signed-off-by: Cliff Liu <donghua.liu@xxxxxxxxxxxxx>
Signed-off-by: He Zhe <Zhe.He@xxxxxxxxxxxxx>
---
Verified the build test.
---
 fs/cifs/misc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 33328eae03d7..c7e2bf7a0a0d 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -464,6 +464,8 @@ 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)
-- 
2.34.1