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Tue, 03 Nov 2026 18:02:49 -0800 (PST) Received: from localhost ([153.61.198.255]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b096b52911sm435986a91.3.2026.11.03.18.02.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2026 18:02:49 -0800 (PST) Content-Type: text/plain; charset=UTF-8 Date: Wed, 04 Nov 2026 02:02:48 +0000 Message-Id: Subject: Re: [PATCH bpf-next v3 06/14] libbpf: Relocate pointers that are stored in arena From: "Alexei Starovoitov" To: , , In-Reply-To: References: <20261104012401.1354861-1-alexei.starovoitov@gmail.com> <20261104012401.1354861-7-alexei.starovoitov@gmail.com> Content-Transfer-Encoding: 8bit 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 On Tue, Nov 03, 2026 at 05:44 PM sashiko-bot@kernel.org wrote: >> + ptrs = libbpf_reallocarray(NULL, nrels, sizeof(*ptrs)); >> + if (!ptrs) >> + return -ENOMEM; >> + obj->arena_ptrs = ptrs; [...] > 1. If multiple SEC_RELO sections target arena_data_shndx, the second call > overwrites obj->arena_ptrs (leaking the prior allocation) and allocates only > nrels entries, while obj->arena_ptr_cnt holds the sum across both calls. When > bpf_object__create_maps() -> relocate_arena_ptrs() later runs: Not a bug. Only a hand-made ELF has two SHT_REL sections for one section. clang emits one for .addr_space.1, and the static linker merges them by name in linker_append_elf_relos(). > 2. If an empty .rel.addr_space.1 section has sh_size == 0 (nrels == 0), > libbpf_reallocarray(NULL, 0, sizeof(*ptrs)) calls realloc(NULL, 0), which may > return NULL and cause bpf_object__collect_arena_relos() to return -ENOMEM. No. Nothing emits an empty SHT_REL section. glibc returns a pointer for realloc(NULL, 0). Where it's NULL the open of such a file fails, and that's fine. I'm replying to a bot hoping that Roman will teach it to learn from maintainers and stop reporting such bugs in libbpf where input is trusted.