From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f77.google.com (mail-ot1-f77.google.com [209.85.210.77]) (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 992E21A6825 for ; Thu, 23 Apr 2026 01:06:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.77 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776906390; cv=none; b=PCfCxYX7/7g5EZMUxy5manjLU0i1aZOBrgDb89ZT1X2iS829EBmN6HGBatrDUl6RjLh9YK3Fn7cmXMLWv+J1OhT3sQUhqGwZiyGSU07Vjq4CBiOn4eMq9u+zFvxFYfgFRQx8RkdWiEKDWjOLQWpW/d1tOWKB8/2f9UbaTMNhMGw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776906390; c=relaxed/simple; bh=vWqOM9nXuwLGUOZ+JxVDQtJNjHxs/osDVjdzuCyp35E=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=p82LltlkLDdslsn/lkyxKfi3DDI2MKJ7/DcNgvteBFoPR5gWKf1TAgLrKGHmIVAjHhlYR8+NZ64yho9DeLS3L2HQ0tH1a9ptogyeJV2CUoIkBWJNItgtsQBmYG6t6GyZ4vtjL6fRw3pBL7Tv/hzEsxngC8rBtJ9ay/bzbfuu87s= 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=209.85.210.77 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-ot1-f77.google.com with SMTP id 46e09a7af769-7d4be1dee67so14913552a34.1 for ; Wed, 22 Apr 2026 18:06:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776906387; x=1777511187; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=zsSvGzVB80tFyVwkB3cRPRPM6dI8of/Q43SEFzEvigI=; b=OrnztPrGYvGUlBn1QoO/4eodUEIXCn2R7BrAHb7sTJDxWyaHRXYQA0I1WWn5cF9NSq kstglstnjNRygvYdjDNR90nB7LfQqaiXVjV+BdRowegY4z2UhPa/9cfDhurTBI2fkChr Y8DJSXp21UdjPVE0qBns+unSHoxLLElD+MK3KNFB25aL9mBtfsiAaQtYZpkJ7eBHckOc lSX30psFeqAhT6pJWOFhjHUgfqaPbuXFAj3lYLnb4COu4zA2S4jTrrLUAbQkn7JRpLNQ FJcbR7npKa9Ss9CMayxc6izlZKFmxsjF+WuyoRMFZn8zopLIHzwnBNZ8gTMx3AHK393f kFiw== X-Forwarded-Encrypted: i=1; AFNElJ8GhIFTURRqtGMhw2QSWRUrJbSm9pQkLGji/Eo/U0y/+C/P+8NVwYXmwILGl42rpPclsICu8yI=@vger.kernel.org X-Gm-Message-State: AOJu0YzTlk3Q5YUE/EpV2AJTxu+BamWTKjvsmzSf0snkU30MfyrDfa+e A6sRbhPUZJ+WgRCZLRQfGJSRtLfyn3FNC+63A4oyVjCjYv4gv03IhnmfL+waT9MTRr2FNxmSxYj aWPZ9vbhj4FQWVU+E8nYx4hAAhe9tBrk5sWnDETExDMaR+d1d+ItrinyMMFg= Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a4a:e844:0:b0:67e:36e9:79a6 with SMTP id 006d021491bc7-69462e48a91mr15566883eaf.19.1776906387619; Wed, 22 Apr 2026 18:06:27 -0700 (PDT) Date: Wed, 22 Apr 2026 18:06:27 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69e97093.050a0220.24bfd3.0048.GAE@google.com> Subject: [syzbot] [net?] KCSAN: data-race in __udp4_lib_mcast_deliver / udp_lib_unhash (3) 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, willemdebruijn.kernel@gmail.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: c23719abc330 Merge tag 'x86-urgent-2026-03-08' of git://gi.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=141b0806580000 kernel config: https://syzkaller.appspot.com/x/.config?x=6b32b22d8934c136 dashboard link: https://syzkaller.appspot.com/bug?extid=04905b8b3523856476c0 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/c0ec3784100d/disk-c23719ab.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/ff5ee751c9be/vmlinux-c23719ab.xz kernel image: https://storage.googleapis.com/syzbot-assets/1dda25fb6996/bzImage-c23719ab.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+04905b8b3523856476c0@syzkaller.appspotmail.com ================================================================== BUG: KCSAN: data-race in __udp4_lib_mcast_deliver / udp_lib_unhash read-write to 0xffff88810194a9c8 of 4 bytes by task 15107 on cpu 0: udp_lib_unhash+0x1f4/0x3e0 net/ipv4/udp.c:2261 sk_common_release+0x7a/0x230 net/core/sock.c:3990 udp_lib_close+0x15/0x20 include/net/udp.h:324 inet_release+0xcd/0xf0 net/ipv4/af_inet.c:437 __sock_release net/socket.c:662 [inline] sock_close+0x6b/0x150 net/socket.c:1455 __fput+0x29b/0x650 fs/file_table.c:469 ____fput+0x1c/0x30 fs/file_table.c:497 task_work_run+0x130/0x1a0 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:67 [inline] exit_to_user_mode_loop+0x1f4/0x6f0 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline] do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff88810194a9c8 of 4 bytes by task 15111 on cpu 1: __udp4_lib_mcast_deliver+0x9a/0x790 net/ipv4/udp.c:2564 __udp4_lib_rcv+0x972/0x1250 net/ipv4/udp.c:2749 udp_rcv+0x4f/0x60 net/ipv4/udp.c:2936 ip_protocol_deliver_rcu+0x3f7/0x790 net/ipv4/ip_input.c:207 ip_local_deliver_finish+0x1fc/0x2f0 net/ipv4/ip_input.c:241 NF_HOOK include/linux/netfilter.h:318 [inline] ip_local_deliver+0xe8/0x1e0 net/ipv4/ip_input.c:262 dst_input include/net/dst.h:480 [inline] ip_sublist_rcv_finish net/ipv4/ip_input.c:584 [inline] ip_list_rcv_finish net/ipv4/ip_input.c:628 [inline] ip_sublist_rcv+0x415/0x6a0 net/ipv4/ip_input.c:644 ip_list_rcv+0x261/0x290 net/ipv4/ip_input.c:678 __netif_receive_skb_list_ptype net/core/dev.c:6207 [inline] __netif_receive_skb_list_core+0x4dc/0x500 net/core/dev.c:6254 __netif_receive_skb_list net/core/dev.c:6306 [inline] netif_receive_skb_list_internal+0x47d/0x5f0 net/core/dev.c:6397 netif_receive_skb_list+0x35/0x220 net/core/dev.c:6449 xdp_recv_frames net/bpf/test_run.c:269 [inline] xdp_test_run_batch net/bpf/test_run.c:350 [inline] bpf_test_run_xdp_live+0x104c/0x1360 net/bpf/test_run.c:379 bpf_prog_test_run_xdp+0x57b/0xa10 net/bpf/test_run.c:1397 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4722 __sys_bpf+0x52e/0x7e0 kernel/bpf/syscall.c:6246 __do_sys_bpf kernel/bpf/syscall.c:6341 [inline] __se_sys_bpf kernel/bpf/syscall.c:6339 [inline] __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6339 x64_sys_call+0x10cb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:322 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x00000001 -> 0x00000000 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 15111 Comm: syz.6.4060 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 ================================================================== --- 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