Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 28 Sep 2022 13:49:19 +0300
From:   Leon Romanovsky <leon@kernel.org>
To:     asmadeus@codewreck.org
Cc:     syzbot <syzbot+67d13108d855f451cafc@syzkaller.appspotmail.com>,
        davem@davemloft.net, edumazet@google.com, ericvh@gmail.com,
        kuba@kernel.org, linux-kernel@vger.kernel.org,
        linux_oss@crudebyte.com, lucho@ionkov.net, netdev@vger.kernel.org,
        pabeni@redhat.com, syzkaller-bugs@googlegroups.com,
        v9fs-developer@lists.sourceforge.net
Subject: Re: [syzbot] KASAN: use-after-free Read in rdma_close
Message-ID: <YzQmr8LVTmUj9+zB@unreal>
References: <00000000000015ac7905e97ebaed@google.com>
 <YzQc2yaDufjp+rHc@unreal>
 <YzQlWq9EOi9jpy46@codewreck.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YzQlWq9EOi9jpy46@codewreck.org>
Precedence: bulk

On Wed, Sep 28, 2022 at 07:43:38PM +0900, asmadeus@codewreck.org wrote:
> Leon Romanovsky wrote on Wed, Sep 28, 2022 at 01:07:23PM +0300:
> > The bug is in commit 3ff51294a055 ("9p: p9_client_create: use p9_client_destroy on failure").
> 
> Thanks for looking
> 
> > It is wrong to call to p9_client_destroy() if clnt->trans_mod->create fails.
> 
> hmm that's a bit broad :)
> 
> But I agree I did get that wrong: trans_mod->close() wasn't called if
> create failed.
> We do want the idr_for_each_entry() that is in p9_client_destroy so
> rather than revert the commit (fix a bug, create a new one..) I'd rather
> split it out in an internal function that takes a 'bool close' or
> something to not duplicate the rest.
> (Bit of a nitpick, sure)

Please do proper unwind without extra variable.

Proper unwind means that you will call to symmetrical functions in
destroy as you used in create:
alloc -> free
create -> close
e.t.c

When you use some global function like you did, there is huge chance
to see unwind bugs.

> 
> I'll send a patch and credit you in Reported-by unless you don't want
> to.
> 
> -- 
> Dominique