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Mon, 02 Nov 2026 04:37:23 -0800 (PST) Received: from [127.0.1.1] ([23.254.208.9]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a428c17bdsm36326095eec.6.2026.11.02.04.37.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Nov 2026 04:37:23 -0800 (PST) From: Qiliang Yuan Date: Mon, 02 Nov 2026 07:37:03 -0500 Subject: [PATCH bpf-next 3/5] bpf: Finalize the verifier log after the runtime is selected X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261102-bpf-blind-nops-fixes-v1-3-844300e42cdb@gmail.com> References: <20261102-bpf-blind-nops-fixes-v1-0-844300e42cdb@gmail.com> In-Reply-To: <20261102-bpf-blind-nops-fixes-v1-0-844300e42cdb@gmail.com> To: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Luis Gerhorst , Henriette Herzog , Anton Protopopov , Xu Kuohai , Hengqi Chen , Shuah Khan Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Qiliang Yuan X-Mailer: b4 0.13.0 bpf_check() finalizes the log, which reports its size in log_true_size, and selects the runtime of the prog after that. For a prog of one function, selecting the runtime blinds the constants. Blinding can log "insn %d cannot be patched due to 16-bit range". The message lands in the buffer, but log_true_size doesn't count it: with a stats-only log, log_true_size is 219 while the log takes 264 bytes. A caller that sizes the buffer from log_true_size loses the message. Finalize the log after __bpf_prog_select_runtime(). Fixes: d9ef13f72711 ("bpf: Pass bpf_verifier_env to JIT") Reported-by: Alexei Starovoitov Closes: https://lore.kernel.org/bpf/DMKHZS5B5CNO.186F6YH1T6YU4@gmail.com/ Signed-off-by: Qiliang Yuan --- kernel/bpf/verifier.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 935b163f81e4b..974dc571eff05 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -24112,11 +24112,6 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, print_verification_stats(env); env->prog->aux->verified_insns = env->insn_processed; - /* preserve original error even if log finalization is successful */ - err = bpf_log_attr_finalize(attr_log, &env->log); - if (err) - ret = err; - if (ret) goto err_release_maps; @@ -24167,6 +24162,14 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, env->prog = __bpf_prog_select_runtime(env, env->prog, &ret); err_release_maps: + /* + * Finalize the log after the runtime is selected, which blinds the + * constants of a prog of one function and can log an error. Preserve + * the original error even if log finalization is successful. + */ + err = bpf_log_attr_finalize(attr_log, &env->log); + if (err) + ret = err; if (ret) release_insn_arrays(env); if (!env->prog->aux->used_maps) -- 2.43.0