From: Martin KaFai Lau <kafai@fb.com>
To: John Fastabend <john.fastabend@gmail.com>
Cc: <jakub@cloudflare.com>, <daniel@iogearbox.net>,
<netdev@vger.kernel.org>, <bpf@vger.kernel.org>, <ast@kernel.org>
Subject: Re: [PATCH 1/2] bpf: sockmap, msg_pop_data can incorrecty set an sge length
Date: Tue, 5 May 2020 11:59:44 -0700 [thread overview]
Message-ID: <20200505185944.wkwu47cat4k2awxr@kafai-mbp> (raw)
In-Reply-To: <158861288359.14306.7654891716919968144.stgit@john-Precision-5820-Tower>
On Mon, May 04, 2020 at 10:21:23AM -0700, John Fastabend wrote:
> When sk_msg_pop() is called where the pop operation is working on
> the end of a sge element and there is no additional trailing data
> and there _is_ data in front of pop, like the following case,
>
>
> |____________a_____________|__pop__|
>
> We have out of order operations where we incorrectly set the pop
> variable so that instead of zero'ing pop we incorrectly leave it
> untouched, effectively. This can cause later logic to shift the
> buffers around believing it should pop extra space. The result is
> we have 'popped' more data then we expected potentially breaking
> program logic.
>
> It took us a while to hit this case because typically we pop headers
> which seem to rarely be at the end of a scatterlist elements but
> we can't rely on this.
>
> Fixes: 7246d8ed4dcce ("bpf: helper to pop data from messages")
> Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
next prev parent reply other threads:[~2020-05-05 19:00 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-04 17:21 [PATCH 0/2] sockmap, fix for some error paths with helpers John Fastabend
2020-05-04 17:21 ` [PATCH 1/2] bpf: sockmap, msg_pop_data can incorrecty set an sge length John Fastabend
2020-05-05 18:59 ` Martin KaFai Lau [this message]
2020-05-04 17:21 ` [PATCH 2/2] bpf: sockmap, bpf_tcp_ingress needs to subtract bytes from sg.size John Fastabend
2020-05-05 19:05 ` Martin KaFai Lau
2020-05-05 9:30 ` [PATCH 0/2] sockmap, fix for some error paths with helpers Jakub Sitnicki
2020-05-05 22:28 ` Daniel Borkmann
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