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From: asmadeus@codewreck.org
To: Leon Romanovsky <leon@kernel.org>
Cc: Tuo Li <islituo@gmail.com>,
	ericvh@gmail.com, lucho@ionkov.net, davem@davemloft.net,
	kuba@kernel.org, v9fs-developer@lists.sourceforge.net,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	baijiaju1990@gmail.com, TOTE Robot <oslab@tsinghua.edu.cn>
Subject: Re: [PATCH] net: 9p: Fix possible null-pointer dereference in p9_cm_event_handler()
Date: Tue, 10 Aug 2021 23:20:24 +0900	[thread overview]
Message-ID: <YRKLKGtxVZAbKVG5@codewreck.org> (raw)
In-Reply-To: <YRKFXpilGXnKZ2yH@unreal>

Leon Romanovsky wrote on Tue, Aug 10, 2021 at 04:55:42PM +0300:
> On Tue, Aug 10, 2021 at 06:20:07AM -0700, Tuo Li wrote:
> > The variable rdma is checked when event->event is equal to 
> > RDMA_CM_EVENT_DISCONNECTED:
> >   if (rdma)
> > 
> > This indicates that it can be NULL. If so, a null-pointer dereference will 
> > occur when calling complete():
> >   complete(&rdma->cm_done);
> > 
> > To fix this possible null-pointer dereference, calling complete() only 
> > when rdma is not NULL.
> 
> You need to explain how is it possible and blindly set if () checks.
> I would say first "if (rdma)" is not needed, but don't know for sure.

Sounds like static analysis because there's a if (rdma) check in
RDMA_CM_EVENT_DISCONNECTED above, so if that needed check then it will
bug right afterwards

I'd tend to agree I don't think it's possible client->trans is null
there (it's filled right after rdma_create_id which defines the handler,
there might be a window where the callback is called before? But as I
understand it shouldn't be called until we resolve address and connect
then later disconnect)

So, I agree with Leon - unless you have a backtrace of a real bug
let's remove the other 'if' if you want to cleanup something for your
robot.

-- 
Dominique

      reply	other threads:[~2021-08-10 14:27 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-10 13:20 Tuo Li
2021-08-10 13:55 ` Leon Romanovsky
2021-08-10 14:20   ` asmadeus [this message]

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