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Message-Id: <20220330123027.25897-1-xiam0nd.tong@gmail.com>
Date: Wed, 30 Mar 2022 20:30:27 +0800
From: Xiaomeng Tong <xiam0nd.tong@...il.com>
To: leon@...nel.org
Cc: bharat@...lsio.com, jgg@...pe.ca, linux-kernel@...r.kernel.org,
linux-rdma@...r.kernel.org, roland@...estorage.com,
stable@...r.kernel.org, vipul@...lsio.com, xiam0nd.tong@...il.com
Subject: Re: [PATCH] cxgb4: cm: fix a incorrect NULL check on list iterator
On Sun, 27 Mar 2022 19:38:31 +0300, Leon Romanovsky wrote:
>
> On Sun, Mar 27, 2022 at 03:35:42PM +0800, Xiaomeng Tong wrote:
> > The bug is here:
> > if (!pdev) {
> >
> > The list iterator value 'pdev' will *always* be set and non-NULL
> > by for_each_netdev(), so it is incorrect to assume that the
> > iterator value will be NULL if the list is empty or no element
> > found (in this case, the check 'if (!pdev)' can be bypassed as
> > it always be false unexpectly).
> >
> > To fix the bug, use a new variable 'iter' as the list iterator,
> > while use the original variable 'pdev' as a dedicated pointer to
> > point to the found element.
>
> I don't think that the description is correct.
> We are talking about loopback interface which received packet, the pdev will always exist.
Do the both conditions impossible?
1. the list is empty or
2. we can not found a pdev due to this check
if (ipv6_chk_addr(&init_net,
(struct in6_addr *)peer_ip,
pdev, 1))
iter, 1))
> Most likely. the check of "if (!pdev)" is to catch impossible situation where IPV6 packet
> was sent over loopback, but IPV6 is not enabled.
--
Xiaomeng Tong
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