From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f80.google.com (mail-oa1-f80.google.com [209.85.160.80]) (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 28A1E472793 for ; Thu, 30 Apr 2026 16:42:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.80 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777567355; cv=none; b=UhhVDNsvjZWKRqmGw/41KHiBPzLk2QpATgdc3vhgdcd8q/RcBxfTc7+cREp5yKCri1izUy3AU60oq3Rq4zPyzQwURUE0PQ1FELly4gUPV2joBEi8XU/YPrOpmjGAhJCRvycdrJeE4MrNBx7BzpxReKysDkP62ntdT1g17U0oj3s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777567355; c=relaxed/simple; bh=rfb+H5qZ2rKtzwKc6euaXaLazpvHhK9GYWqWgLYYd8s=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=a/Fmn7xN9eGOnXg9BS6pC3J7SzTbpJmtoytS00uGHAqXDamufWzfB+qCCTVd13h1pTVHyFAoQMvNQJQGqWTMm6NeFicNhHoUesp5YWxlYuYlChAQk499HR+cf3Xd00GtteOnABFaH7yvQ6OS8IqobFBnBCw/lxzwSndIwnnZeiE= 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=209.85.160.80 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-oa1-f80.google.com with SMTP id 586e51a60fabf-42343e87c3aso1881646fac.0 for ; Thu, 30 Apr 2026 09:42:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777567349; x=1778172149; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=/87TmCa3Z2FxwWDx4aZtt07eMNF7YEg9iirIvSv7caM=; b=BlK9nqY3K1UaHLfjXOoFtAz7lLi4O7wN18sxIny9LLEyocXPDavF9mLXGHlYtDqSnQ 3v/r/jXkh+d1zs9qAhRFRb4vg6ckApVLINIRhUUARWG2qja82dLLHFQcPixrI1udCQSM 5jaeCtaiXoasC8rL2yapmXaTASzHbP/xe4W7lzNDq8TtiO4NxWOsRcRhnaQZaVk5FXro oLlfAKf9PI6gDOESvWVGx+z1gHbF/iZjLASaEwPULTPfIeD+DHMZk9I3iqhLStgArjmR I8bc83UNyRfpC1DpSH3a/Vgk2RGiyt/RhJk8eDg8blYzmcA/QkbFlNK2M1miqZ2KgemZ +SWA== X-Forwarded-Encrypted: i=1; AFNElJ+oOLTR3g8LdM047r0wrWj9FZ383I8cBxXjeAgu5IouJLNNUFLWX3IxTu0sHevauKywLKORgdcaOsTeWgo=@vger.kernel.org X-Gm-Message-State: AOJu0YwXrfPwntky8ErXG/jGxBiV3OWIPYnHy8rZq0fiTLO5E93f85W/ m6k9p2zOdcXPzOoYjlSLavToXEa/VXq/vxBpr36YBzbU8llb2hhdjg1HzHJwFD3jzw13+NO8dm0 H7xSiZBdntWphCKrAA7jlyI8RsY8SflfaCF5Xm4kWxLUmNcGqlaz3Rivvig0= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:2207:b0:696:1860:8baf with SMTP id 006d021491bc7-6967a510993mr2004307eaf.20.1777567349578; Thu, 30 Apr 2026 09:42:29 -0700 (PDT) Date: Thu, 30 Apr 2026 09:42:29 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69f38675.050a0220.3cbe47.0002.GAE@google.com> Subject: [syzbot] [net?] KCSAN: data-race in igmp_rcv / igmp_rcv (2) 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: 2d1373e4246d Merge tag 'for-7.0-rc4-tag' of git://git.kern.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1184a8da580000 kernel config: https://syzkaller.appspot.com/x/.config?x=3a78dd265deac3a9 dashboard link: https://syzkaller.appspot.com/bug?extid=ae9a171f239b14485310 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/b2aee7aa6da1/disk-2d1373e4.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/6cbfa1602880/vmlinux-2d1373e4.xz kernel image: https://storage.googleapis.com/syzbot-assets/52fe8db03e03/bzImage-2d1373e4.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+ae9a171f239b14485310@syzkaller.appspotmail.com ================================================================== BUG: KCSAN: data-race in igmp_rcv / igmp_rcv read to 0xffff88810a66f058 of 8 bytes by task 5213 on cpu 1: igmp_heard_query net/ipv4/igmp.c:1025 [inline] igmp_rcv+0x10af/0x1200 net/ipv4/igmp.c:1103 ip_protocol_deliver_rcu+0x421/0x790 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_rcv_finish+0x188/0x1a0 net/ipv4/ip_input.c:453 NF_HOOK include/linux/netfilter.h:318 [inline] ip_rcv+0x62/0x160 net/ipv4/ip_input.c:573 __netif_receive_skb_one_core net/core/dev.c:6164 [inline] __netif_receive_skb net/core/dev.c:6277 [inline] netif_receive_skb_internal net/core/dev.c:6363 [inline] netif_receive_skb+0x137/0x530 net/core/dev.c:6422 tun_rx_batched+0x106/0x440 drivers/net/tun.c:1485 tun_get_user+0x2011/0x27c0 drivers/net/tun.c:1953 tun_chr_write_iter+0x15e/0x210 drivers/net/tun.c:1999 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x5a6/0x9f0 fs/read_write.c:688 ksys_write+0xdc/0x1a0 fs/read_write.c:740 __do_sys_write fs/read_write.c:751 [inline] __se_sys_write fs/read_write.c:748 [inline] __x64_sys_write+0x40/0x50 fs/read_write.c:748 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2 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 write to 0xffff88810a66f058 of 8 bytes by task 5212 on cpu 0: igmp_heard_query net/ipv4/igmp.c:1026 [inline] igmp_rcv+0x10eb/0x1200 net/ipv4/igmp.c:1103 ip_protocol_deliver_rcu+0x421/0x790 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_rcv_finish+0x188/0x1a0 net/ipv4/ip_input.c:453 NF_HOOK include/linux/netfilter.h:318 [inline] ip_rcv+0x62/0x160 net/ipv4/ip_input.c:573 __netif_receive_skb_one_core net/core/dev.c:6164 [inline] __netif_receive_skb net/core/dev.c:6277 [inline] netif_receive_skb_internal net/core/dev.c:6363 [inline] netif_receive_skb+0x137/0x530 net/core/dev.c:6422 tun_rx_batched+0x106/0x440 drivers/net/tun.c:1485 tun_get_user+0x2011/0x27c0 drivers/net/tun.c:1953 tun_chr_write_iter+0x15e/0x210 drivers/net/tun.c:1999 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x5a6/0x9f0 fs/read_write.c:688 ksys_write+0xdc/0x1a0 fs/read_write.c:740 __do_sys_write fs/read_write.c:751 [inline] __se_sys_write fs/read_write.c:748 [inline] __x64_sys_write+0x40/0x50 fs/read_write.c:748 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2 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: 0x00000000000003e8 -> 0x0000000000000000 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 5212 Comm: syz.1.463 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