linux-kernel - Re: [PATCH] rxrpc: fix bad unlock balance in rxrpc_do

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Date:   Mon, 22 Aug 2022 09:48:14 +0100
From:   David Howells <dhowells@...hat.com>
To:     Hawkins Jiawei <yin31149@...il.com>
Cc:     dhowells@...hat.com,
        syzbot+7f0483225d0c94cb3441@...kaller.appspotmail.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
Subject: Re: [PATCH] rxrpc: fix bad unlock balance in rxrpc_do_sendmsg

Hawkins Jiawei <yin31149@...il.com> wrote:

> -		if (mutex_lock_interruptible(&call->user_mutex) < 0)
> +		if (mutex_lock_interruptible(&call->user_mutex) < 0) {
> +			mutex_lock(&call->user_mutex);

Yeah, as Khalid points out that kind of makes the interruptible lock
pointless.  Either rxrpc_send_data() needs to return a separate indication
that we returned without the lock held or it needs to always drop the lock on
error (at least for ERESTARTSYS/EINTR) which can be checked for higher up.

David