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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: ast@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org,
	anatoly.trosinenko@gmail.com
Subject: Re: [PATCH bpf] bpf: Fix passing modified ctx to ld/abs/ind instruction
Date: Mon, 6 Jan 2020 14:24:55 -0800	[thread overview]
Message-ID: <20200106222454.6ajkzw4s2vfq2mye@ast-mbp> (raw)
In-Reply-To: <20200106215157.3553-1-daniel@iogearbox.net>

On Mon, Jan 06, 2020 at 10:51:57PM +0100, Daniel Borkmann wrote:
> Anatoly has been fuzzing with kBdysch harness and reported a KASAN
> slab oob in one of the outcomes:
> 
> After further debugging, turns out while in case of other helper functions
> we disallow passing modified ctx, the special case of ld/abs/ind instruction
> which has similar semantics (except r6 being the ctx argument) is missing
> such check. Modified ctx is impossible here as bpf_skb_load_helper_8_no_cache()
> and others are expecting skb fields in original position, hence, add
> check_ctx_reg() to reject any modified ctx. Issue was first introduced back
> in f1174f77b50c ("bpf/verifier: rework value tracking").
> 
> Fixes: f1174f77b50c ("bpf/verifier: rework value tracking")
> Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Applied, Thanks

      reply	other threads:[~2020-01-06 22:24 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-06 21:51 [PATCH bpf] bpf: Fix passing modified ctx to ld/abs/ind instruction Daniel Borkmann
2020-01-06 22:24 ` Alexei Starovoitov [this message]

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