From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-149.mta0.migadu.com [91.218.175.149]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E29E33F58C4 for ; Mon, 31 Aug 2026 12:27:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.149 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788179242; cv=none; b=IZFxk9voikzOZxqDRofE467Ey1fcFvD1iv2MHcb9m1M//DEMnwXewCgkTAbi00ahRdrYj51zAszpvklrBu9R7YDcT2OhZJ3WfjyUbItRXSL7nPHxsD6rYCF8OFjb2P442c7mHGC5qvWARd3tvqhJDxwr3f8x+lm+L8662IvmNzk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788179242; c=relaxed/simple; bh=OhUAGuLpEUtGnu4qFuSxitUETrm9FnNYjqGDp4Zm3Sg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ea3AwBjiOhuSgz3ym7H7y8ebhFdrbNgfpTUaDmS+1vPI+Yk45D8GQouoC6WuLmdBBoVQv8tkzBJXhGMhbHJXLYJHrTWK7IZ4HFzKe42bl3A9fV4riDS8ltbe3vGuratOyCzHbBemkprVTOvLYJWLc/HjJWhBFKhXnF3F2VeL6ic= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=UcFJ+UhH; arc=none smtp.client-ip=91.218.175.149 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="UcFJ+UhH" X-Envelope-To: linux-kselftest@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=OhUAGuLpEUtGnu4qFuSxitUETrm9FnNYjqGDp4Zm3Sg=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788179238; v=1; x=1788784038; b=UcFJ+UhHE04pM3wJToZLi1qJpHoz9wCESCjXPucx4341eJfBGgN+v4c8uds52U/PTnODz8Jf UW44Eg8FpyuxbDvkF2umebTsEJ3vaJaRtaUURmdqhovSDBCMZhV7W41TDUQGz39D4VYSolFXFO4 vXAw6w5Gv0aeg0m3Tr4GWFC0= X-Envelope-To: linux-kselftest@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 6820a5db4ae73fcc; Mon, 31 Aug 2026 12:27:18 +0000 X-Mizu-Trace-ID: 6820a5db4ae73fcc X-Migadu-Flow: FLOW_OUT Message-ID: <309536ab-86b3-47a6-a420-c460447f6c46@linux.dev> Date: Mon, 31 Aug 2026 20:27:11 +0800 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf v3 1/5] bpf: Reject key-less BTF for hash maps To: bot+bpf-ci@kernel.org, jiayuan.chen@linux.dev, bpf@vger.kernel.org Cc: syzbot+37b56485bbbf90ad8489@syzkaller.appspotmail.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, shuah@kernel.org, yatsenko@meta.com, alan.maguire@oracle.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, martin.lau@kernel.org, mason@kernel.org References: <20260831110314.150870-2-jiayuan.chen@linux.dev> <9ed4c84cc7d723627f10b9b5d1dafb9b72d3e0bcff6db149d7605f5d9ad8c7b1@mail.kernel.org> From: Jiayuan Chen In-Reply-To: <9ed4c84cc7d723627f10b9b5d1dafb9b72d3e0bcff6db149d7605f5d9ad8c7b1@mail.kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 8/31/26 8:05 PM, bot+bpf-ci@kernel.org 写道: >> map_check_btf() allows a key-less BTF (btf_key_type_id == 0) only for >> maps that have a ->map_check_btf callback, and leaves the actual >> decision to that callback. Hash maps used to have no ->map_check_btf, >> so a key-less BTF was rejected outright. >> >> That changed when htab and rhtab gained a ->map_check_btf to register a >> dtor - htab in commit 1df97a7453ee ("bpf: Register dtor for freeing >> special fields") and rhtab in commit 6905f8601298 ("bpf: Allow special >> fields in resizable hashtab"). Neither looks at the key, so a key-less >> hash map now passes map_check_btf() and gets created. Reading it back >> through bpffs feeds the key type_id 0 into btf_type_seq_show(); >> btf_type_by_id() returns the void type, kind_ops[BTF_KIND_UNKN] is NULL, >> and btf_type_show() dereferences it: >> >> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] >> RIP: 0010:btf_type_show+0x223/0x2e0 kernel/bpf/btf.c:8232 >> Call Trace: >> >> btf_type_seq_show_flags+0xca/0x120 kernel/bpf/btf.c:8250 >> htab_map_seq_show_elem+0x12e/0x350 kernel/bpf/hashtab.c:1669 >> map_seq_show+0x13d/0x1e0 kernel/bpf/inode.c:293 >> seq_read_iter+0x93f/0x1270 fs/seq_file.c:196 >> seq_read+0x344/0x4d0 fs/seq_file.c:163 >> vfs_read+0x1e4/0xb40 fs/read_write.c:572 >> __x64_sys_pread64+0x1eb/0x250 fs/read_write.c:769 >> do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> > The call trace appears to be edited from the original syzbot report. > The original report (6a8f4e88.27659fcc.2ceef7.0008.GAE@google.com) > includes these additional frames between map_seq_show and seq_read_iter: > > traverse.part.0.constprop.0+0x107/0x650 fs/seq_file.c:112 > traverse fs/seq_file.c:99 [inline] > > and also includes the inline frames for the pread64 syscall path: > > ksys_pread64 fs/read_write.c:760 [inline] > __do_sys_pread64 fs/read_write.c:769 [inline] > __se_sys_pread64 fs/read_write.c:766 [inline] I edited it intentional‌ly to avoid breaking the format rule.