From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f205.google.com (mail-oi1-f205.google.com [209.85.167.205]) (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 BB1A31F2B8D for ; Tue, 27 Jan 2026 04:27:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.205 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769488048; cv=none; b=m6Jr5CrtZXCuNjve3R6s5OqlSSKrpcD+yLQuMmxrYkCd/jUlGq//AAh94JliTdGQHQvMKuKGbrJ8INA0djv3stJ+6YQZNgkWzbxWot+pEBOVGCqS+E2xl2qFS2mMQ5QaLMl+knW/51vYYQ2ZJzI+VBx5JWCtShDuUkogXffThWQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769488048; c=relaxed/simple; bh=YuFUtxbGs8XoO6mBjA0KxEddLWHuYp+dvmesQhy1vNk=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=gha7gd/y3s75E4US7STZUOACuORA5S/9kLK4BGBeNf3Uv3plyFRD0yDYFHRKSu3OW98T1eRqDNi5FChB0ROGPaxKIBckpStTsE92+KZhxIdxojqvXFmBje2nm1F87SsFbpBdY5I29bQ33FsQUEZIB5q2+cHBcGZcYpuwLnBusUM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.167.205 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oi1-f205.google.com with SMTP id 5614622812f47-45c91358254so14100890b6e.0 for ; Mon, 26 Jan 2026 20:27:26 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769488046; x=1770092846; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=QGPXctGzCvQhO6o5zNaSG+4khA0zm/mQn3hOs7bG9JY=; b=L+LzT3yX7u6ac/nQrzv4i3s0bvwYOptMUwIh+mwxOtHMLBXtfXThR+zDRtxIRLvPOz BhyvKIK5+wL2FjHjFiwnw2zXJIyhEzmXoISA6E7/WDcUk6XFcy+9/EY0hPfiCAhE4F3p uerJqE9NBXEYF+D76JVEQ2t56qp3OJQkU/OtxYJ4Lbu0m8XalUSPE/xJi67rVvjeYKsT gs2E2UY0OqUZ7Qt//vDyOueZ7z/DrpgtauM37sL3BdpJGZ+u0Z2EJMMBubZP25rmN3gl 99dZxvXbXS56W5COXiSqfjU+0Z3g4jnqMCuDsJV9Nz/wGqt1wkQWkZjDSxyH978TscQV JGdQ== X-Forwarded-Encrypted: i=1; AJvYcCU0IT1XuoiLs/+Wa8WhwK5Ckz8PqP+D37FK19TQ9te7W4WfAIi9wckKoHDj5Ng2pct763hg5xs=@vger.kernel.org X-Gm-Message-State: AOJu0YyN/V3xgiQhCpGxWfI0rsp7/MCCKv+CS7+Llnvp4og+JRUW7OI/ rCme/1oWkBR/r/1s5njnswKqyZt49KQt1ko9uUcdaKjW+3SJb3KRhOpyzPG6YcPMCf55kF+nY3X UlqKJEZfn1vmC5+GLUqdwzE3wdfxwR7v/7oJPp/1YjExrmOuokTYCzIIKV+I= Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:1998:b0:65b:5745:6123 with SMTP id 006d021491bc7-662f202860emr291800eaf.16.1769488045785; Mon, 26 Jan 2026 20:27:25 -0800 (PST) Date: Mon, 26 Jan 2026 20:27:25 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69783ead.050a0220.c9109.0013.GAE@google.com> Subject: [syzbot] [net?] KCSAN: data-race in fib_table_lookup / fib_table_lookup (4) From: syzbot To: davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, horms@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: fcb70a56f4d8 Merge tag 'vfs-6.19-rc8.fixes' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10c8a05a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8e27f4588a0f2183 dashboard link: https://syzkaller.appspot.com/bug?extid=d24f940f770afda885cf compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/f09fa28d6094/disk-fcb70a56.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/d7b2aaa28bcd/vmlinux-fcb70a56.xz kernel image: https://storage.googleapis.com/syzbot-assets/aa72cf9601a0/bzImage-fcb70a56.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+d24f940f770afda885cf@syzkaller.appspotmail.com ================================================================== BUG: KCSAN: data-race in fib_table_lookup / fib_table_lookup write to 0xffff88811b06a7fa of 1 bytes by task 4167 on cpu 0: fib_alias_accessed net/ipv4/fib_lookup.h:32 [inline] fib_table_lookup+0x361/0xd60 net/ipv4/fib_trie.c:1565 fib_lookup include/net/ip_fib.h:390 [inline] ip_route_output_key_hash_rcu+0x378/0x1380 net/ipv4/route.c:2814 ip_route_output_key_hash net/ipv4/route.c:2705 [inline] __ip_route_output_key include/net/route.h:169 [inline] ip_route_output_flow+0x65/0x110 net/ipv4/route.c:2932 udp_sendmsg+0x13c3/0x15d0 net/ipv4/udp.c:1450 inet_sendmsg+0xac/0xd0 net/ipv4/af_inet.c:859 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0x53a/0x600 net/socket.c:2592 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646 __sys_sendmmsg+0x185/0x320 net/socket.c:2735 __do_sys_sendmmsg net/socket.c:2762 [inline] __se_sys_sendmmsg net/socket.c:2759 [inline] __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2759 x64_sys_call+0x1e28/0x3000 arch/x86/include/generated/asm/syscalls_64.h:308 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff88811b06a7fa of 1 bytes by task 4168 on cpu 1: fib_alias_accessed net/ipv4/fib_lookup.h:31 [inline] fib_table_lookup+0x338/0xd60 net/ipv4/fib_trie.c:1565 fib_lookup include/net/ip_fib.h:390 [inline] ip_route_output_key_hash_rcu+0x378/0x1380 net/ipv4/route.c:2814 ip_route_output_key_hash net/ipv4/route.c:2705 [inline] __ip_route_output_key include/net/route.h:169 [inline] ip_route_output_flow+0x65/0x110 net/ipv4/route.c:2932 udp_sendmsg+0x13c3/0x15d0 net/ipv4/udp.c:1450 inet_sendmsg+0xac/0xd0 net/ipv4/af_inet.c:859 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0x53a/0x600 net/socket.c:2592 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646 __sys_sendmmsg+0x185/0x320 net/socket.c:2735 __do_sys_sendmmsg net/socket.c:2762 [inline] __se_sys_sendmmsg net/socket.c:2759 [inline] __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2759 x64_sys_call+0x1e28/0x3000 arch/x86/include/generated/asm/syscalls_64.h:308 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x00 -> 0x01 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 4168 Comm: syz.4.206 Not tainted syzkaller #0 PREEMPT(voluntary) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 ================================================================== --- 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 report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup