diff options
| author | Daniel Borkmann <daniel@iogearbox.net> | 2017-12-22 16:29:05 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-12-25 14:23:47 +0100 |
| commit | 3695b3b18519099224efbc5875569d2cb6da256d (patch) | |
| tree | 03b70a41cbc9ddd7f4f9b11c2b95c3035b0aa8cc /kernel/bpf | |
| parent | d75d3ee237cee9068022117e059b64bbab617f3d (diff) | |
bpf: fix incorrect sign extension in check_alu_op()
From: Jann Horn <jannh@google.com>
[ Upstream commit 95a762e2c8c942780948091f8f2a4f32fce1ac6f ]
Distinguish between
BPF_ALU64|BPF_MOV|BPF_K (load 32-bit immediate, sign-extended to 64-bit)
and BPF_ALU|BPF_MOV|BPF_K (load 32-bit immediate, zero-padded to 64-bit);
only perform sign extension in the first case.
Starting with v4.14, this is exploitable by unprivileged users as long as
the unprivileged_bpf_disabled sysctl isn't set.
Debian assigned CVE-2017-16995 for this issue.
v3:
- add CVE number (Ben Hutchings)
Fixes: 484611357c19 ("bpf: allow access into map value arrays")
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b03af36b8e87..8b1ebe4c6aba 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1790,10 +1790,17 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) /* case: R = imm * remember the value we stored into this reg */ + u64 imm; + + if (BPF_CLASS(insn->code) == BPF_ALU64) + imm = insn->imm; + else + imm = (u32)insn->imm; + regs[insn->dst_reg].type = CONST_IMM; - regs[insn->dst_reg].imm = insn->imm; - regs[insn->dst_reg].max_value = insn->imm; - regs[insn->dst_reg].min_value = insn->imm; + regs[insn->dst_reg].imm = imm; + regs[insn->dst_reg].max_value = imm; + regs[insn->dst_reg].min_value = imm; } } else if (opcode > BPF_END) { |