45 lines
1.5 KiB
Diff
45 lines
1.5 KiB
Diff
From: Jann Horn <jannh@google.com>
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Date: Mon, 18 Dec 2017 20:11:54 -0800
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Subject: [2/9] bpf: fix incorrect sign extension in check_alu_op()
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Origin: https://git.kernel.org/linus/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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---
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kernel/bpf/verifier.c | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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--- a/kernel/bpf/verifier.c
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+++ b/kernel/bpf/verifier.c
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@@ -2401,7 +2401,13 @@ static int check_alu_op(struct bpf_verif
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* remember the value we stored into this reg
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*/
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regs[insn->dst_reg].type = SCALAR_VALUE;
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- __mark_reg_known(regs + insn->dst_reg, insn->imm);
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+ if (BPF_CLASS(insn->code) == BPF_ALU64) {
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+ __mark_reg_known(regs + insn->dst_reg,
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+ insn->imm);
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+ } else {
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+ __mark_reg_known(regs + insn->dst_reg,
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+ (u32)insn->imm);
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+ }
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}
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} else if (opcode > BPF_END) {
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