linux-kernel - [PATCH 3.16 26/83] SMB3: Fix deadlock in validate negotiate hits reconnect

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Date:   Wed, 20 Nov 2019 15:37:36 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Steve French" <stfrench@...rosoft.com>,
        "Ronnie Sahlberg" <lsahlber@...hat.com>,
        "Pavel Shilovsky" <pshilov@...rosoft.com>
Subject: [PATCH 3.16 26/83] SMB3: Fix deadlock in validate negotiate hits
 reconnect

3.16.78-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Pavel Shilovsky <pshilov@...rosoft.com>

commit e99c63e4d86d3a94818693147b469fa70de6f945 upstream.

Currently we skip SMB2_TREE_CONNECT command when checking during
reconnect because Tree Connect happens when establishing
an SMB session. For SMB 3.0 protocol version the code also calls
validate negotiate which results in SMB2_IOCL command being sent
over the wire. This may deadlock on trying to acquire a mutex when
checking for reconnect. Fix this by skipping SMB2_IOCL command
when doing the reconnect check.

Signed-off-by: Pavel Shilovsky <pshilov@...rosoft.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/cifs/smb2pdu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -171,7 +171,7 @@ smb2_reconnect(__le16 smb2_command, stru
 	if (tcon == NULL)
 		return 0;
 
-	if (smb2_command == SMB2_TREE_CONNECT)
+	if (smb2_command == SMB2_TREE_CONNECT || smb2_command == SMB2_IOCTL)
 		return 0;
 
 	if (tcon->tidStatus == CifsExiting) {