From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E488CC71153 for ; Tue, 29 Aug 2023 18:30:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238108AbjH2Sa1 (ORCPT ); Tue, 29 Aug 2023 14:30:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238499AbjH2SaS (ORCPT ); Tue, 29 Aug 2023 14:30:18 -0400 Received: from out-253.mta0.migadu.com (out-253.mta0.migadu.com [91.218.175.253]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16225CD8 for ; Tue, 29 Aug 2023 11:30:06 -0700 (PDT) Message-ID: <2e260b7c-2a89-2d0c-afb5-708c34230db2@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1693333802; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=z9qhS9JnvDdEoGnT4EeYHMwTRSvFUoem4eApRVql4dg=; b=KvMhiKrMJ6fsV4goHvB6nER+PmVpg5unIoRCmrDH4ZmWWXrBjkIpdDB65S4iFAYEtizr4Z RA17fWrCt12qth1jWM2Kh66m/RxGUmAfndvPWH4dCAIyo27MqFcJ5hZP5+RvHDeoDlcBQF K00WKUc1/1seLt1xEoDhDPpRM6IE7e0= Date: Tue, 29 Aug 2023 14:29:56 -0400 MIME-Version: 1.0 Reply-To: yonghong.song@linux.dev Subject: Re: [syzbot] [bpf?] KCSAN: data-race in bpf_percpu_array_update / bpf_percpu_array_update (2) To: syzbot , andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, haoluo@google.com, john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org, linux-kernel@vger.kernel.org, martin.lau@linux.dev, sdf@google.com, song@kernel.org, syzkaller-bugs@googlegroups.com, yhs@fb.com References: <000000000000d87a7f06040c970c@google.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <000000000000d87a7f06040c970c@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/29/23 5:39 AM, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 727dbda16b83 Merge tag 'hardening-v6.6-rc1' of git://git.k.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=136f39dfa80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=dea9c2ce3f646a25 > dashboard link: https://syzkaller.appspot.com/bug?extid=97522333291430dd277f > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/9923a023ab11/disk-727dbda1.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/650dbc695d77/vmlinux-727dbda1.xz > kernel image: https://storage.googleapis.com/syzbot-assets/361da71276bf/bzImage-727dbda1.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+97522333291430dd277f@syzkaller.appspotmail.com > > ================================================================== > BUG: KCSAN: data-race in bpf_percpu_array_update / bpf_percpu_array_update > > write to 0xffffe8fffe7425d8 of 8 bytes by task 8257 on cpu 1: > bpf_long_memcpy include/linux/bpf.h:428 [inline] > bpf_obj_memcpy include/linux/bpf.h:441 [inline] > copy_map_value_long include/linux/bpf.h:464 [inline] > bpf_percpu_array_update+0x3bb/0x500 kernel/bpf/arraymap.c:380 > bpf_map_update_value+0x190/0x370 kernel/bpf/syscall.c:175 > generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1749 > bpf_map_do_batch+0x2df/0x3d0 kernel/bpf/syscall.c:4648 > __sys_bpf+0x28a/0x780 > __do_sys_bpf kernel/bpf/syscall.c:5241 [inline] > __se_sys_bpf kernel/bpf/syscall.c:5239 [inline] > __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5239 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > write to 0xffffe8fffe7425d8 of 8 bytes by task 8268 on cpu 0: > bpf_long_memcpy include/linux/bpf.h:428 [inline] > bpf_obj_memcpy include/linux/bpf.h:441 [inline] > copy_map_value_long include/linux/bpf.h:464 [inline] > bpf_percpu_array_update+0x3bb/0x500 kernel/bpf/arraymap.c:380 > bpf_map_update_value+0x190/0x370 kernel/bpf/syscall.c:175 > generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1749 > bpf_map_do_batch+0x2df/0x3d0 kernel/bpf/syscall.c:4648 > __sys_bpf+0x28a/0x780 > __do_sys_bpf kernel/bpf/syscall.c:5241 [inline] > __se_sys_bpf kernel/bpf/syscall.c:5239 [inline] > __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5239 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > value changed: 0x0000000000000000 -> 0xfffffff000002788 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 0 PID: 8268 Comm: syz-executor.4 Not tainted 6.5.0-syzkaller-00453-g727dbda16b83 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023 > ================================================================== This case is with two tasks doing bpf_map batch update together for the same map and key. > write to 0xffffe8fffe7425d8 of 8 bytes by task 8257 on cpu 1: > write to 0xffffe8fffe7425d8 of 8 bytes by task 8268 on cpu 0: So concurrency is introduced by user applications. In my opinion, this probably not an issue from kernel perspective. > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the bug is already fixed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want to overwrite bug's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the bug is a duplicate of another bug, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup >