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CIFS: Fix race condition on RFC1002_NEGATIVE_SESSION_RESPONSE

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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.
This commit is contained in:
Federico Sauter 2015-03-17 17:45:28 +01:00 committed by Steve French
parent b29103076b
commit 4afe260bab
1 changed files with 2 additions and 1 deletions
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3
fs/cifs/connect.c
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@ -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;