From: Federico Sauter <fsauter@innominate.com>
Date: Tue, 17 Mar 2015 16:45:28 +0000 (+0100)
Subject: CIFS: Fix race condition on RFC1002_NEGATIVE_SESSION_RESPONSE
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=4afe260bab50290a05e5732570329a530ed023f3;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

CIFS: Fix race condition on RFC1002_NEGATIVE_SESSION_RESPONSE

This patch fixes a race condition that occurs when connecting
to a NT 3.51 host without specifying a NetBIOS name.
In that case a RFC1002_NEGATIVE_SESSION_RESPONSE is received
and the SMB negotiation is reattempted, but under some conditions
it leads SendReceive() to hang forever while waiting for srv_mutex.
This, in turn, sets the calling process to an uninterruptible sleep
state and makes it unkillable.

The solution is to unlock the srv_mutex acquired in the demux
thread *before* going to sleep (after the reconnect error) and
before reattempting the connection.
---

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index f3bfe08e177b..8383d5ea4202 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -386,6 +386,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 		rc = generic_ip_connect(server);
 		if (rc) {
 			cifs_dbg(FYI, "reconnect error %d\n", rc);
+			mutex_unlock(&server->srv_mutex);
 			msleep(3000);
 		} else {
 			atomic_inc(&tcpSesReconnectCount);
@@ -393,8 +394,8 @@ cifs_reconnect(struct TCP_Server_Info *server)
 			if (server->tcpStatus != CifsExiting)
 				server->tcpStatus = CifsNeedNegotiate;
 			spin_unlock(&GlobalMid_Lock);
+			mutex_unlock(&server->srv_mutex);
 		}
-		mutex_unlock(&server->srv_mutex);
 	} while (server->tcpStatus == CifsNeedReconnect);
 
 	return rc;