From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jann Horn <jannh@google.com>,
davem@davemloft.net, kuznet@ms2.inr.ac.ru,
yoshfuji@linux-ipv6.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] tcp: don't read out-of-bounds opsize
Date: Fri, 20 Apr 2018 07:21:35 -0700 [thread overview]
Message-ID: <552d49b6-1b6e-c320-b56a-a119e360f1d7@gmail.com> (raw)
In-Reply-To: <20180420135730.44921-1-jannh@google.com>
On 04/20/2018 06:57 AM, Jann Horn wrote:
> The old code reads the "opsize" variable from out-of-bounds memory (first
> byte behind the segment) if a broken TCP segment ends directly after an
> opcode that is neither EOL nor NOP.
>
> The result of the read isn't used for anything, so the worst thing that
> could theoretically happen is a pagefault; and since the physmap is usually
> mostly contiguous, even that seems pretty unlikely.
>
No page fault possible, because tcp headers are in skb->head
And we have 'struct skb_shared_info' at the end of skb->head anyway.
But, yes, reading some extra bytes with random content is possible.
next prev parent reply other threads:[~2018-04-20 14:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-20 13:57 [PATCH net] tcp: don't read out-of-bounds opsize Jann Horn
2018-04-20 14:21 ` Eric Dumazet [this message]
2018-04-23 13:52 ` David Miller
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