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Wed, 24 Sep 2025 09:43:47 -0700 (PDT) Received: from localhost ([41.210.143.179]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-46e2aae3d58sm43152915e9.21.2025.09.24.09.43.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Sep 2025 09:43:47 -0700 (PDT) Date: Wed, 24 Sep 2025 19:43:42 +0300 From: Dan Carpenter To: Eduard Zingerman Cc: bpf@vger.kernel.org Subject: [bug report] bpf: callchain sensitive stack liveness tracking using CFG Message-ID: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hello Eduard Zingerman, Commit b3698c356ad9 ("bpf: callchain sensitive stack liveness tracking using CFG") from Sep 18, 2025 (linux-next), leads to the following Smatch static checker warning: kernel/bpf/liveness.c:527 propagate_to_outer_instance() error: 'outer_instance' dereferencing possible ERR_PTR() kernel/bpf/liveness.c 514 static int propagate_to_outer_instance(struct bpf_verifier_env *env, 515 struct func_instance *instance) 516 { 517 struct callchain *callchain = &instance->callchain; 518 u32 this_subprog_start, callsite, frame; 519 struct func_instance *outer_instance; 520 struct per_frame_masks *insn; 521 int err; 522 523 this_subprog_start = callchain_subprog_start(callchain); 524 outer_instance = get_outer_instance(env, instance); This needs if (IS_ERR(outer_instance)) check. 525 callsite = callchain->callsites[callchain->curframe - 1]; 526 --> 527 reset_stack_write_marks(env, outer_instance, callsite); ^^^^^^^^^^^^^^ 528 for (frame = 0; frame < callchain->curframe; frame++) { 529 insn = get_frame_masks(instance, frame, this_subprog_start); 530 if (!insn) 531 continue; 532 bpf_mark_stack_write(env, frame, insn->must_write_acc); 533 err = mark_stack_read(env, outer_instance, frame, callsite, insn->live_before); 534 if (err) 535 return err; 536 } 537 commit_stack_write_marks(env, outer_instance); 538 return 0; 539 } regards, dan carpenter