From: Daniel Borkmann via iovisor-dev <iovisor-dev-9jONkmmOlFHEE9lA1F8Ukti2O/JbrIOy@public•gmane.org>
To: Edward Cree <ecree-s/n/eUQHGBpZroRs9YW3xA@public•gmane.org>,
davem-fT/PcQaiUtIeIZ0/mPfg9Q@public•gmane.org,
Alexei Starovoitov
<alexei.starovoitov-Re5JQEeQqe8AvxtiuMwx3w@public•gmane.org>,
Alexei Starovoitov <ast-b10kYP2dOMg@public•gmane.org>
Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
iovisor-dev
<iovisor-dev-9jONkmmOlFHEE9lA1F8Ukti2O/JbrIOy@public•gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
josef-DigfWCa+lFGyeJad7bwFQA@public•gmane.org
Subject: Re: [PATCH net 1/2] selftests/bpf: subtraction bounds test
Date: Fri, 21 Jul 2017 16:29:22 +0200 [thread overview]
Message-ID: <59720FC2.9070301@iogearbox.net> (raw)
In-Reply-To: <a12c5a59-d2e0-5866-d225-501d19a3ec7b-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org>
On 07/21/2017 03:36 PM, Edward Cree wrote:
> There is a bug in the verifier's handling of BPF_SUB: [a,b] - [c,d] yields
> was [a-c, b-d] rather than the correct [a-d, b-c]. So here is a test
> which, with the bogus handling, will produce ranges of [0,0] and thus
> allowed accesses; whereas the correct handling will give a range of
> [-255, 255] (and hence the right-shift will give a range of [0, 255]) and
> the accesses will be rejected.
>
> Signed-off-by: Edward Cree <ecree-s/n/eUQHGBpZroRs9YW3xA@public•gmane.org>
Acked-by: Daniel Borkmann <daniel-FeC+5ew28dpmcu3hnIyYJQ@public•gmane.org>
> tools/testing/selftests/bpf/test_verifier.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> index af7d173..addea82 100644
> --- a/tools/testing/selftests/bpf/test_verifier.c
> +++ b/tools/testing/selftests/bpf/test_verifier.c
> @@ -5980,6 +5980,34 @@ static struct bpf_test tests[] = {
> .result = REJECT,
> .result_unpriv = REJECT,
> },
> + {
> + "subtraction bounds (map value)",
> + .insns = {
> + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
> + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
> + BPF_LD_MAP_FD(BPF_REG_1, 0),
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
> + BPF_FUNC_map_lookup_elem),
> + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 9),
> + BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_0, 0),
> + BPF_JMP_IMM(BPF_JGT, BPF_REG_1, 0xff, 7),
> + BPF_LDX_MEM(BPF_B, BPF_REG_3, BPF_REG_0, 1),
> + BPF_JMP_IMM(BPF_JGT, BPF_REG_3, 0xff, 5),
> + BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_3),
> + BPF_ALU64_IMM(BPF_RSH, BPF_REG_1, 56),
> + BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1),
> + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + },
> + .fixup_map1 = { 3 },
> + .errstr_unpriv = "R0 pointer arithmetic prohibited",
> + .errstr = "R0 min value is negative, either use unsigned index or do a if (index >=0) check.",
> + .result = REJECT,
> + .result_unpriv = REJECT,
> + },
> };
>
> static int probe_filter_length(const struct bpf_insn *fp)
>
next prev parent reply other threads:[~2017-07-21 14:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-21 13:35 [PATCH net 0/2] bpf: fix verifier min/max handling in BPF_SUB Edward Cree via iovisor-dev
2017-07-21 13:36 ` [PATCH net 1/2] selftests/bpf: subtraction bounds test Edward Cree
[not found] ` <a12c5a59-d2e0-5866-d225-501d19a3ec7b-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org>
2017-07-21 14:29 ` Daniel Borkmann via iovisor-dev [this message]
[not found] ` <2ebcb201-2f18-7276-f4f9-f2bbaffae179-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org>
2017-07-21 13:37 ` [PATCH net 2/2] bpf/verifier: fix min/max handling in BPF_SUB Edward Cree via iovisor-dev
[not found] ` <e3fa964f-54f2-7310-59d1-41a4b7ad9a5b-s/n/eUQHGBpZroRs9YW3xA@public.gmane.org>
2017-07-21 14:30 ` Daniel Borkmann via iovisor-dev
2017-07-21 15:54 ` [PATCH net 0/2] bpf: fix verifier " Nadav Amit via iovisor-dev
2017-07-24 21:03 ` David Miller via iovisor-dev
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