linux-kernel - fix locking unbalance in irda

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Message-ID: <20110412221254.GA23906@redhat.com>
Date:	Tue, 12 Apr 2011 18:12:55 -0400
From:	Dave Jones <davej@...hat.com>
To:	netdev@...r.kernel.org
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: fix locking unbalance in irda_sendmsg

5b40964eadea40509d353318d2c82e8b7bf5e8a5 introduced a path where
we have a locking unbalance.  If we pass invalid flags, we unlock
a socket we never locked, resulting in this...

=====================================
[ BUG: bad unlock balance detected! ]
-------------------------------------
trinity/20101 is trying to release lock (sk_lock-AF_IRDA) at:
[<ffffffffa057f001>] irda_sendmsg+0x207/0x21d [irda]
but there are no more locks to release!

other info that might help us debug this:
no locks held by trinity/20101.

stack backtrace:
Pid: 20101, comm: trinity Not tainted 2.6.39-rc3+ #3
Call Trace:
 [<ffffffffa057f001>] ? irda_sendmsg+0x207/0x21d [irda]
 [<ffffffff81085041>] print_unlock_inbalance_bug+0xc7/0xd2
 [<ffffffffa057f001>] ? irda_sendmsg+0x207/0x21d [irda]
 [<ffffffff81086aca>] lock_release+0xcf/0x18e
 [<ffffffff813ed190>] release_sock+0x2d/0x155
 [<ffffffffa057f001>] irda_sendmsg+0x207/0x21d [irda]
 [<ffffffff813e9f8c>] __sock_sendmsg+0x69/0x75
 [<ffffffff813ea105>] sock_sendmsg+0xa1/0xb6
 [<ffffffff81100ca3>] ? might_fault+0x5c/0xac
 [<ffffffff81086b7c>] ? lock_release+0x181/0x18e
 [<ffffffff81100cec>] ? might_fault+0xa5/0xac
 [<ffffffff81100ca3>] ? might_fault+0x5c/0xac
 [<ffffffff81133b94>] ? fcheck_files+0xb9/0xf0
 [<ffffffff813f387a>] ? copy_from_user+0x2f/0x31
 [<ffffffff813f3b70>] ? verify_iovec+0x52/0xa6
 [<ffffffff813eb4e3>] sys_sendmsg+0x23a/0x2b8
 [<ffffffff81086b7c>] ? lock_release+0x181/0x18e
 [<ffffffff810773c6>] ? up_read+0x28/0x2c
 [<ffffffff814bec3d>] ? do_page_fault+0x360/0x3b4
 [<ffffffff81087043>] ? trace_hardirqs_on_caller+0x10b/0x12f
 [<ffffffff810458aa>] ? finish_task_switch+0xb2/0xe3
 [<ffffffff8104583e>] ? finish_task_switch+0x46/0xe3
 [<ffffffff8108364a>] ? trace_hardirqs_off_caller+0x33/0x90
 [<ffffffff814bbaf9>] ? retint_swapgs+0x13/0x1b
 [<ffffffff81087043>] ? trace_hardirqs_on_caller+0x10b/0x12f
 [<ffffffff810a9dd3>] ? audit_syscall_entry+0x11c/0x148
 [<ffffffff8125609e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
 [<ffffffff814c22c2>] system_call_fastpath+0x16/0x1b

Signed-off-by: Dave Jones <davej@...hat.com>

diff --git a/net/irda/af_irda.c b/net/irda/af_irda.c
index c9890e2..cc61697 100644
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -1297,8 +1297,7 @@ static int irda_sendmsg(struct kiocb *iocb, struct socket *sock,
 	/* Note : socket.c set MSG_EOR on SEQPACKET sockets */
 	if (msg->msg_flags & ~(MSG_DONTWAIT | MSG_EOR | MSG_CMSG_COMPAT |
 			       MSG_NOSIGNAL)) {
-		err = -EINVAL;
-		goto out;
+		return -EINVAL;
 	}
 
 	lock_sock(sk);
--
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