netdev - Re: [PATCH net-next] selftests/bpf: add a test case to check verifier pointer arithmetic

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Date:   Wed, 03 May 2017 09:52:37 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     ast@...com
Cc:     daniel@...earbox.net, netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH net-next] selftests/bpf: add a test case to check
 verifier pointer arithmetic

From: Alexei Starovoitov <ast@...com>
Date: Tue, 2 May 2017 19:58:14 -0700

> From: Yonghong Song <yhs@...com>
> 
> With clang/llvm 4.0+, the test case is able to generate
> the following pattern:
> ....
> 440: (b7) r1 = 15
> 441: (05) goto pc+73
> 515: (79) r6 = *(u64 *)(r10 -152)
> 516: (bf) r7 = r10
> 517: (07) r7 += -112
> 518: (bf) r2 = r7
> 519: (0f) r2 += r1
> 520: (71) r1 = *(u8 *)(r8 +0)
> 521: (73) *(u8 *)(r2 +45) = r1
> ....
> 
> commit 332270fdc8b6 ("bpf: enhance verifier to understand stack
> pointer arithmetic") improved verifier to handle such a pattern.
> This patch adds a C test case to actually generate such a pattern.
> A dummy tracepoint interface is used to load the program
> into the kernel.
> 
> Signed-off-by: Yonghong Song <yhs@...com>
> Acked-by: Martin KaFai Lau <kafai@...com>
> Acked-by: Daniel Borkmann <daniel@...earbox.net>
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>

Applied.