69 lines
2.4 KiB
Diff
69 lines
2.4 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Jann Horn <jannh@google.com>
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Date: Thu, 4 Jan 2018 08:01:22 -0600
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Subject: [PATCH] bpf: fix incorrect sign extension in check_alu_op()
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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[ Upstream commit 95a762e2c8c942780948091f8f2a4f32fce1ac6f ]
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Distinguish between
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BPF_ALU64|BPF_MOV|BPF_K (load 32-bit immediate, sign-extended to 64-bit)
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and BPF_ALU|BPF_MOV|BPF_K (load 32-bit immediate, zero-padded to 64-bit);
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only perform sign extension in the first case.
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Starting with v4.14, this is exploitable by unprivileged users as long as
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the unprivileged_bpf_disabled sysctl isn't set.
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Debian assigned CVE-2017-16995 for this issue.
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v3:
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- add CVE number (Ben Hutchings)
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Fixes: 484611357c19 ("bpf: allow access into map value arrays")
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Signed-off-by: Jann Horn <jannh@google.com>
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Acked-by: Edward Cree <ecree@solarflare.com>
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Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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CVE-2017-16995
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Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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(cherry picked from commit 868c88129c7567525dbde3cb6989a5acd478bd80)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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kernel/bpf/verifier.c | 15 +++++++++++----
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1 file changed, 11 insertions(+), 4 deletions(-)
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diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
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index 4321625fe32a..cdfa07a4ef27 100644
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--- a/kernel/bpf/verifier.c
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+++ b/kernel/bpf/verifier.c
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@@ -2048,12 +2048,19 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
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/* case: R = imm
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* remember the value we stored into this reg
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*/
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+ u64 imm;
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+
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+ if (BPF_CLASS(insn->code) == BPF_ALU64)
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+ imm = insn->imm;
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+ else
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+ imm = (u32)insn->imm;
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+
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regs[insn->dst_reg].type = CONST_IMM;
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- regs[insn->dst_reg].imm = insn->imm;
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+ regs[insn->dst_reg].imm = imm;
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regs[insn->dst_reg].id = 0;
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- regs[insn->dst_reg].max_value = insn->imm;
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- regs[insn->dst_reg].min_value = insn->imm;
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- regs[insn->dst_reg].min_align = calc_align(insn->imm);
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+ regs[insn->dst_reg].max_value = imm;
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+ regs[insn->dst_reg].min_value = imm;
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+ regs[insn->dst_reg].min_align = calc_align(imm);
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regs[insn->dst_reg].value_from_signed = false;
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}
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--
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2.14.2
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