From: Ronnie Sahlberg <lsahlber@redhat.com>
Date: Wed, 5 Jun 2019 10:15:34 +1000
Subject: [PATCH] cifs: fix panic in smb2_reconnect
Git-commit: 0ff2b018b02f89da26a616e0148582321a00fd99
Patch-mainline: v5.2-rc5
References: bsc#1144333

RH Bugzilla: 1702264

We need to protect so that the call to smb2_reconnect() in
smb2_reconnect_server() does not end up freeing the session
because it can lead to a use after free and crash.

Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
 fs/cifs/smb2pdu.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 29b699d532ef..75311a8a68bf 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -3114,9 +3114,14 @@ void smb2_reconnect_server(struct work_struct *work)
 				tcon_exist = true;
 			}
 		}
+		/*
+		 * IPC has the same lifetime as its session and uses its
+		 * refcount.
+		 */
 		if (ses->tcon_ipc && ses->tcon_ipc->need_reconnect) {
 			list_add_tail(&ses->tcon_ipc->rlist, &tmp_list);
 			tcon_exist = true;
+			ses->ses_count++;
 		}
 	}
 	/*
@@ -3135,7 +3140,10 @@ void smb2_reconnect_server(struct work_struct *work)
 		else
 			resched = true;
 		list_del_init(&tcon->rlist);
-		cifs_put_tcon(tcon);
+		if (tcon->ipc)
+			cifs_put_smb_ses(tcon->ses);
+		else
+			cifs_put_tcon(tcon);
 	}
 
 	cifs_dbg(FYI, "Reconnecting tcons finished\n");
-- 
2.22.0