From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f200.google.com (mail-oi1-f200.google.com [209.85.167.200]) (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 DD1ED394797 for ; Sat, 17 Oct 2026 03:09:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792206563; cv=none; b=Ajeg2p5Fu7NRiS9EHcTQvyeTtzDlvYEq2YLVouDuggIt05Vx1Y7ZWVwV6flzu5drpZIB1ap34w+1r6BPx5klDdQ83g4Du1xSYM7lcxlSsjfXHzwe9DOgPoUl5nOqMM/bFwkMzkDiMF/V5xNaSteDNGfLnNXRlKLo53UX9E7zA4o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792206563; c=relaxed/simple; bh=qWZscB2I+FYzj/bKFGPuKuzE61mBCR8+wImSbMhOBwk=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=Xtcw76H/J7cdLzlixW37fBGthfVpYaFXT+rR7E3h4v2FTGIB/5oKJsysDzbTq9vNJ2EBPbBPu/j6yJlOABpqSE1yqHU5fHXZNz+/x3ln22BznGGoW95JRIZa9dCSV4He8rL7y0hNxOqblSG+9PDPl0vFzMqin7K2ux/UrRpVg+4= 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=209.85.167.200 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-f200.google.com with SMTP id 5614622812f47-4c7f887ac6bso896777b6e.3 for ; Fri, 16 Oct 2026 20:09:21 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1792206561; x=1792811361; h=content-type:to:from:subject:message-id:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=JaJZcBIKqUWusrosJzXIs+je6PTOrghJY1sZP6GKQWI=; b=ZV30NAY1PZsSwTx0HAzL83S3ha7gbr53+hAbrNKnr2WvxHkMI/g3soEFgEIOAk05yB U7w6RhOmxD/G9o+ALpLMIFB+q0XA3nY3zuZUgqPFXZj6wcpQZI/co+b7C5nH9wM1+zD7 cu/8iAdyybeEo6M2Yqj6NlQWIx+/ZPN9ED1D14z4qjfhf9bEy1hwinX2aUlCg8ox/DtE 1EsE4sKqDLiyVXyAMtSxgGnr4X1rRIOl30bRgGBsRWslWr1nlJtHQavYQp+ANTpCLJ4X Z21Gwo1HTWJGN/bY4uousb6ZQ4ZMqFaiZU1pRztZClmUJIsNjKFSK5A/+XfDqHC7b/y9 dt+w== X-Forwarded-Encrypted: i=1; AKwUvBzCon2hADkIhdDqe3trItpVoHPkdpRapnV4Yv6Kex92unaWYQN5F1OD/0R11wXX42cNGx0XBtM=@vger.kernel.org X-Gm-Message-State: AFq9FYK0oVMsi2Sc424wXHKIv4jfAKw3NcPcgRgnjpzia5wZ2vhfLUyN OejRhjDWjSM5dcUboQX9QIv19pGwvndTyDOY5Rn9NhO+11bd5idXYKBMymBvBG8ibb9DQ/aO773 jWlC3nfJiHdC/v+L95t+iQQPsKLVbrrQUz9nufgAHH9+DVLpEH/9Pu0iux/U= Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:1488:b0:4cb:f21b:6f8e with SMTP id 5614622812f47-53ccfcb392dmr1461275b6e.33.1792206560901; Fri, 16 Oct 2026 20:09:20 -0700 (PDT) Date: Fri, 16 Oct 2026 20:09:20 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ad2e6e0.6814cce4.34c49f.0026.GAE@google.com> Subject: [syzbot] [x25?] possible deadlock in lapb_connect_request From: syzbot To: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-x25@vger.kernel.org, ms@dev.tdt.de, 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: 24a19b953e2a Linux 7.3-rc7 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=101e883c580000 kernel config: https://syzkaller.appspot.com/x/.config?x=129d675874dbf896 dashboard link: https://syzkaller.appspot.com/bug?extid=8328573e4d0514392471 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/c36b6926be3e/disk-24a19b95.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/413d898eaf27/vmlinux-24a19b95.xz kernel image: https://storage.googleapis.com/syzbot-assets/ada3e66b70fc/bzImage-24a19b95.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+8328573e4d0514392471@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.5.1726/12729 is trying to acquire lock: ffff8880793f6dc0 (&lapb->lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] ffff8880793f6dc0 (&lapb->lock){+.-.}-{3:3}, at: lapb_connect_request+0x5e/0x1a0 net/lapb/lapb_iface.c:293 but task is already holding lock: ffff88802bd78f00 (&lapbeth->up_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] ffff88802bd78f00 (&lapbeth->up_lock){+.-.}-{3:3}, at: lapbeth_xmit+0x24/0x250 drivers/net/wan/lapbether.c:191 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&lapbeth->up_lock){+.-.}-{3:3}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:182 [inline] _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:205 spin_lock_bh include/linux/spinlock.h:353 [inline] lapbeth_xmit+0x24/0x250 drivers/net/wan/lapbether.c:191 __netdev_start_xmit include/linux/netdevice.h:5432 [inline] netdev_start_xmit include/linux/netdevice.h:5441 [inline] xmit_one net/core/dev.c:3953 [inline] dev_hard_start_xmit+0x121/0x760 net/core/dev.c:3969 __dev_queue_xmit+0x1c25/0x4a40 net/core/dev.c:4958 dev_queue_xmit include/linux/netdevice.h:3464 [inline] tx+0xc4/0x130 drivers/block/aoe/aoenet.c:62 kthread+0x1d8/0x3c0 drivers/block/aoe/aoecmd.c:1241 kthread+0x373/0x450 kernel/kthread.c:436 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (_xmit_X25#2){+.-.}-{3:3}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __raw_spin_lock include/linux/spinlock_api_smp.h:190 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:173 spin_lock include/linux/spinlock.h:347 [inline] __netif_tx_lock include/linux/netdevice.h:4841 [inline] __dev_queue_xmit+0x1ac6/0x4a40 net/core/dev.c:4952 neigh_output include/net/neighbour.h:560 [inline] ip_finish_output2+0x851/0x2400 net/ipv4/ip_output.c:236 __ip_finish_output.part.0+0x444/0x6f0 net/ipv4/ip_output.c:314 __ip_finish_output net/ipv4/ip_output.c:302 [inline] ip_finish_output net/ipv4/ip_output.c:324 [inline] NF_HOOK_COND include/linux/netfilter.h:314 [inline] ip_output+0x39b/0xc10 net/ipv4/ip_output.c:437 dst_output include/net/dst.h:471 [inline] ip_local_out+0x193/0x1f0 net/ipv4/ip_output.c:131 iptunnel_xmit+0x722/0xd30 net/ipv4/ip_tunnel_core.c:97 ip_tunnel_xmit+0x1b91/0x3210 net/ipv4/ip_tunnel.c:848 __gre_xmit+0x91a/0xc90 net/ipv4/ip_gre.c:488 gre_tap_xmit+0x44e/0x700 net/ipv4/ip_gre.c:783 __netdev_start_xmit include/linux/netdevice.h:5432 [inline] netdev_start_xmit include/linux/netdevice.h:5441 [inline] xmit_one net/core/dev.c:3953 [inline] dev_hard_start_xmit+0x121/0x760 net/core/dev.c:3969 sch_direct_xmit+0x1b2/0xc70 net/sched/sch_generic.c:372 __dev_xmit_skb net/core/dev.c:4277 [inline] __dev_queue_xmit+0x2812/0x4a40 net/core/dev.c:4916 lapb_data_transmit+0x96/0xc0 net/lapb/lapb_iface.c:447 lapb_transmit_buffer+0xce/0x3a0 net/lapb/lapb_out.c:149 lapb_send_control+0x1ce/0x330 net/lapb/lapb_subr.c:251 lapb_establish_data_link+0xeb/0x110 net/lapb/lapb_out.c:163 lapb_device_event+0x315/0x580 net/lapb/lapb_iface.c:512 notifier_call_chain+0x99/0x3f0 kernel/notifier.c:85 call_netdevice_notifiers_info+0xbe/0x110 net/core/dev.c:2275 call_netdevice_notifiers_extack net/core/dev.c:2313 [inline] call_netdevice_notifiers net/core/dev.c:2327 [inline] __dev_notify_flags+0x22c/0x4b0 net/core/dev.c:9896 netif_change_flags+0x108/0x160 net/core/dev.c:9925 dev_change_flags+0xba/0x260 net/core/dev_api.c:68 devinet_ioctl+0x110b/0x1f10 net/ipv4/devinet.c:1199 inet_ioctl+0x3aa/0x3f0 net/ipv4/af_inet.c:1009 sock_do_ioctl+0x118/0x280 net/socket.c:1325 sock_ioctl+0x599/0x6b0 net/socket.c:1446 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&lapb->lock){+.-.}-{3:3}: check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209 check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:182 [inline] _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:205 spin_lock_bh include/linux/spinlock.h:353 [inline] lapb_connect_request+0x5e/0x1a0 net/lapb/lapb_iface.c:293 lapbeth_xmit+0x1cb/0x250 drivers/net/wan/lapbether.c:205 __netdev_start_xmit include/linux/netdevice.h:5432 [inline] netdev_start_xmit include/linux/netdevice.h:5441 [inline] xmit_one net/core/dev.c:3953 [inline] dev_hard_start_xmit+0x121/0x760 net/core/dev.c:3969 __dev_queue_xmit+0x1c25/0x4a40 net/core/dev.c:4958 dev_queue_xmit include/linux/netdevice.h:3464 [inline] x25_establish_link+0x16f/0x1d0 net/x25/x25_dev.c:170 x25_transmit_link+0x92/0x100 net/x25/x25_link.c:218 x25_write_internal+0x522/0xc80 net/x25/x25_subr.c:255 x25_connect+0x728/0x1080 net/x25/af_x25.c:810 connect_socket net/socket.c:2141 [inline] connect_socket net/socket.c:2131 [inline] __sys_connect_file+0x146/0x1a0 net/socket.c:2166 __sys_connect+0x141/0x170 net/socket.c:2183 __do_sys_connect net/socket.c:2189 [inline] __se_sys_connect net/socket.c:2186 [inline] __x64_sys_connect+0x72/0xb0 net/socket.c:2186 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &lapb->lock --> _xmit_X25#2 --> &lapbeth->up_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&lapbeth->up_lock); lock(_xmit_X25#2); lock(&lapbeth->up_lock); lock(&lapb->lock); *** DEADLOCK *** locks held by syz.5.1726/12729: 4, last CPU#1: #0: ffff88805f65e260 (sk_lock-AF_X25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline] #0: ffff88805f65e260 (sk_lock-AF_X25){+.+.}-{0:0}, at: x25_connect+0xba/0x1080 net/x25/af_x25.c:751 #1: ffffffff8fdec580 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #1: ffffffff8fdec580 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline] #1: ffffffff8fdec580 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x296/0x4a40 net/core/dev.c:4872 #2: ffff8880257f8958 (_xmit_X25#2){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline] #2: ffff8880257f8958 (_xmit_X25#2){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4841 [inline] #2: ffff8880257f8958 (_xmit_X25#2){+.-.}-{3:3}, at: __dev_queue_xmit+0x1ac6/0x4a40 net/core/dev.c:4952 #3: ffff88802bd78f00 (&lapbeth->up_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] #3: ffff88802bd78f00 (&lapbeth->up_lock){+.-.}-{3:3}, at: lapbeth_xmit+0x24/0x250 drivers/net/wan/lapbether.c:191 stack backtrace: CPU: 1 UID: 0 PID: 12729 Comm: syz.5.1726 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209 check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:182 [inline] _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:205 spin_lock_bh include/linux/spinlock.h:353 [inline] lapb_connect_request+0x5e/0x1a0 net/lapb/lapb_iface.c:293 lapbeth_xmit+0x1cb/0x250 drivers/net/wan/lapbether.c:205 __netdev_start_xmit include/linux/netdevice.h:5432 [inline] netdev_start_xmit include/linux/netdevice.h:5441 [inline] xmit_one net/core/dev.c:3953 [inline] dev_hard_start_xmit+0x121/0x760 net/core/dev.c:3969 __dev_queue_xmit+0x1c25/0x4a40 net/core/dev.c:4958 dev_queue_xmit include/linux/netdevice.h:3464 [inline] x25_establish_link+0x16f/0x1d0 net/x25/x25_dev.c:170 x25_transmit_link+0x92/0x100 net/x25/x25_link.c:218 x25_write_internal+0x522/0xc80 net/x25/x25_subr.c:255 x25_connect+0x728/0x1080 net/x25/af_x25.c:810 connect_socket net/socket.c:2141 [inline] connect_socket net/socket.c:2131 [inline] __sys_connect_file+0x146/0x1a0 net/socket.c:2166 __sys_connect+0x141/0x170 net/socket.c:2183 __do_sys_connect net/socket.c:2189 [inline] __se_sys_connect net/socket.c:2186 [inline] __x64_sys_connect+0x72/0xb0 net/socket.c:2186 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f9e4619e1d9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f9e443d5028 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 00007f9e46426090 RCX: 00007f9e4619e1d9 RDX: 0000000000000012 RSI: 0000200000003340 RDI: 000000000000000a RBP: 00007f9e46235888 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f9e46426128 R14: 00007f9e46426090 R15: 00007ffe340b8688 --- 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