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| author | Daniel Borkmann <daniel@iogearbox.net> | 2017-12-22 16:23:05 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-12-25 14:26:32 +0100 |
| commit | 6e12ea4fb45ca86cdd7425276b6993455fee947a (patch) | |
| tree | 6226760084a3be2a60260c60d46a509213c6e8e1 | |
| parent | 4d54f7df5131d67f653f674003ec5f52c9818b53 (diff) | |
| download | linux-stable-6e12ea4fb45ca86cdd7425276b6993455fee947a.tar.gz linux-stable-6e12ea4fb45ca86cdd7425276b6993455fee947a.tar.bz2 linux-stable-6e12ea4fb45ca86cdd7425276b6993455fee947a.zip | |
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>
| -rw-r--r-- | kernel/bpf/verifier.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c6ec04f94525..2811ced3c2a9 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2374,7 +2374,13 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) * remember the value we stored into this reg */ regs[insn->dst_reg].type = SCALAR_VALUE; - __mark_reg_known(regs + insn->dst_reg, insn->imm); + if (BPF_CLASS(insn->code) == BPF_ALU64) { + __mark_reg_known(regs + insn->dst_reg, + insn->imm); + } else { + __mark_reg_known(regs + insn->dst_reg, + (u32)insn->imm); + } } } else if (opcode > BPF_END) { |