From: Daniel Borkmann <daniel@iogearbox.net> mainline inclusion from mainline-v5.13-rc7 commit fe9a5ca7e370e613a9a75a13008a3845ea759d6e category: bugfix bugzilla: NA CVE: CVE-2021-33624 -------------------------------- ... in such circumstances, we do not want to mark the instruction as seen given the goal is still to jmp-1 rewrite/sanitize dead code, if it is not reachable from the non-speculative path verification. We do however want to verify it for safety regardless. With the patch as-is all the insns that have been marked as seen before the patch will also be marked as seen after the patch (just with a potentially different non-zero count). An upcoming patch will also verify paths that are unreachable in the non-speculative domain, hence this extension is needed. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: John Fastabend <john.fastabend@gmail.com> Reviewed-by: Benedict Schlueter <benedict.schlueter@rub.de> Reviewed-by: Piotr Krysiuk <piotras@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Conflicts: kernel/bpf/verifier.c pass_cnt is not introduced in kernel-4.19. Signed-off-by: He Fengqing <hefengqing@huawei.com> Reviewed-by: Kuohai Xu <xukuohai@huawei.com> Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- kernel/bpf/verifier.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a218cfdbc5805..bc62a9d395359 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2932,6 +2932,19 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env, return !ret ? REASON_STACK : 0; } +static void sanitize_mark_insn_seen(struct bpf_verifier_env *env) +{ + struct bpf_verifier_state *vstate = env->cur_state; + + /* If we simulate paths under speculation, we don't update the + * insn as 'seen' such that when we verify unreachable paths in + * the non-speculative domain, sanitize_dead_code() can still + * rewrite/sanitize them. + */ + if (!vstate->speculative) + env->insn_aux_data[env->insn_idx].seen = true; +} + static int sanitize_err(struct bpf_verifier_env *env, const struct bpf_insn *insn, int reason, const struct bpf_reg_state *off_reg, @@ -5466,7 +5479,7 @@ static int do_check(struct bpf_verifier_env *env) } regs = cur_regs(env); - env->insn_aux_data[env->insn_idx].seen = true; + sanitize_mark_insn_seen(env); if (class == BPF_ALU || class == BPF_ALU64) { err = check_alu_op(env, insn); @@ -5687,7 +5700,7 @@ static int do_check(struct bpf_verifier_env *env) return err; env->insn_idx++; - env->insn_aux_data[env->insn_idx].seen = true; + sanitize_mark_insn_seen(env); } else { verbose(env, "invalid BPF_LD mode\n"); return -EINVAL; -- 2.25.1