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bpf: Do not mark insn as seen under speculative path verification
... 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>
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@ -6572,6 +6572,19 @@ do_sim:
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return !ret ? REASON_STACK : 0;
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}
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static void sanitize_mark_insn_seen(struct bpf_verifier_env *env)
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{
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struct bpf_verifier_state *vstate = env->cur_state;
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/* If we simulate paths under speculation, we don't update the
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* insn as 'seen' such that when we verify unreachable paths in
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* the non-speculative domain, sanitize_dead_code() can still
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* rewrite/sanitize them.
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*/
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if (!vstate->speculative)
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env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
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}
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static int sanitize_err(struct bpf_verifier_env *env,
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const struct bpf_insn *insn, int reason,
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const struct bpf_reg_state *off_reg,
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@ -10630,7 +10643,7 @@ static int do_check(struct bpf_verifier_env *env)
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}
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regs = cur_regs(env);
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env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
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sanitize_mark_insn_seen(env);
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prev_insn_idx = env->insn_idx;
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if (class == BPF_ALU || class == BPF_ALU64) {
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@ -10857,7 +10870,7 @@ process_bpf_exit:
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return err;
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env->insn_idx++;
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env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
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sanitize_mark_insn_seen(env);
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} else {
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verbose(env, "invalid BPF_LD mode\n");
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return -EINVAL;
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@ -12712,6 +12725,9 @@ static void free_states(struct bpf_verifier_env *env)
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* insn_aux_data was touched. These variables are compared to clear temporary
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* data from failed pass. For testing and experiments do_check_common() can be
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* run multiple times even when prior attempt to verify is unsuccessful.
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*
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* Note that special handling is needed on !env->bypass_spec_v1 if this is
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* ever called outside of error path with subsequent program rejection.
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*/
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static void sanitize_insn_aux_data(struct bpf_verifier_env *env)
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{
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