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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a97d38c583sm9336845e9.15.2026.10.27.19.15.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Oct 2026 19:15:15 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: sashiko-reviews@lists.linux.dev Cc: bpf@vger.kernel.org Subject: Re: [RFC PATCH bpf-next v1 05/11] bpf: Let the callback of bpf_loop unwind Date: Wed, 28 Oct 2026 03:15:14 +0100 Message-ID: <20261028021514.1203900-5-memxor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: <25728094090d9bf3e4cd88feecec336f0493a5a9.1793147364.git.memxor@gmail.com> X-Mailing-List: bpf@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: 8bit On Wed Oct 28, 2026 at 2:19 AM CET, sashiko-bot wrote: > [...] > [Severity: Critical] > When helper_has_cb_pad(BPF_FUNC_loop) returns true, can inline_bpf_loop() in > kernel/bpf/fixups.c emit a live BPF_JMP32_A instruction that jumps to a dead > landing pad which is subsequently removed by dead code elimination, or leave a > stray BPF_UNWIND_GOTO after a load instruction? Same as on 04/11, fixed in the next version: the inlined loop gets a pad only when the verifier saw the pad of the caller, and the unwind_goto after the call becomes a no-op jump either way. > [...] > [Severity: Medium] > What happens in prepare_func_exit() in kernel/bpf/verifier.c when a bpf_loop() > callback subprogram with a 9 to 16 byte BTF return type (ret_reg_pair == true) > unwinds via unwind_exit? Same as on 03/11: a callback hands over r0 alone in the next version, whatever its prototype says. > [...]