linux-kernel - Re: [syzbot] WARNING: bad unlock balance in rxrpc_do

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Date:   Mon, 22 Aug 2022 01:17:51 +0600
From:   Khalid Masum <khalid.masum.92@...il.com>
To:     syzbot+7f0483225d0c94cb3441@...kaller.appspotmail.com
Cc:     David Howells <dhowells@...hat.com>,
        Marc Dionne <marc.dionne@...istor.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        paskripkin@...il.com, skhan@...uxfoundation.org,
        18801353760@....com, Hawkins Jiawei <yin31149@...il.com>,
        Khalid Masum <khalid.masum.92@...il.com>
Subject: Re: [syzbot] WARNING: bad unlock balance in rxrpc_do_sendmsg

Maybe we do not need to lock since no other timer_schedule needs 
it. 

Test if this fixes the issue.
---
#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 568035b01cfb
 net/rxrpc/sendmsg.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index 1d38e279e2ef..640e2ab2cc35 100644
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -51,10 +51,8 @@ static int rxrpc_wait_for_tx_window_intr(struct rxrpc_sock *rx,
 			return sock_intr_errno(*timeo);
 
 		trace_rxrpc_transmit(call, rxrpc_transmit_wait);
-		mutex_unlock(&call->user_mutex);
 		*timeo = schedule_timeout(*timeo);
-		if (mutex_lock_interruptible(&call->user_mutex) < 0)
-			return sock_intr_errno(*timeo);
+		return sock_intr_errno(*timeo);
 	}
 }
 
-- 
2.37.1