From: Daniel Borkmann daniel@iogearbox.net
commit fe9a5ca7e370e613a9a75a13008a3845ea759d6e upstream
... 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 [OP: - env->pass_cnt is not used in 5.4, so adjust sanitize_mark_insn_seen() to assign "true" instead - drop sanitize_insn_aux_data() comment changes, as the function is not present in 5.4] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/verifier.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
--- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4435,6 +4435,19 @@ do_sim: 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, @@ -7790,7 +7803,7 @@ static int do_check(struct bpf_verifier_ }
regs = cur_regs(env); - env->insn_aux_data[env->insn_idx].seen = true; + sanitize_mark_insn_seen(env); prev_insn_idx = env->insn_idx;
if (class == BPF_ALU || class == BPF_ALU64) { @@ -8025,7 +8038,7 @@ process_bpf_exit: 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;