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Thu, 27 Mar 2025 07:44:01 -0700 (PDT) Received: from localhost ([2601:646:9e00:f56e:123b:cea3:439a:b3e3]) by smtp.gmail.com with UTF8SMTPSA id 41be03b00d2f7-af8a27db649sm12814821a12.10.2025.03.27.07.44.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Mar 2025 07:44:00 -0700 (PDT) Date: Thu, 27 Mar 2025 07:43:59 -0700 From: Stanislav Fomichev To: Eric Dumazet Cc: syzbot , andrew+netdev@lunn.ch, andrew@lunn.ch, davem@davemloft.net, eric.dumazet@gmail.com, horms@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-x25@vger.kernel.org, lkp@intel.com, llvm@lists.linux.dev, ms@dev.tdt.de, netdev@vger.kernel.org, oe-kbuild-all@lists.linux.dev, pabeni@redhat.com, sdf@fomichev.me, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [x25?] possible deadlock in lapbeth_device_event Message-ID: References: <67cd611c.050a0220.14db68.0073.GAE@google.com> <67e55c12.050a0220.2f068f.002c.GAE@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 03/27, Eric Dumazet wrote: > On Thu, Mar 27, 2025 at 3:36 PM Stanislav Fomichev wrote: > > > > On 03/27, syzbot wrote: > > > syzbot has found a reproducer for the following issue on: > > > > > > HEAD commit: 1a9239bb4253 Merge tag 'net-next-6.15' of git://git.kernel.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=15503804580000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=95c3bbe7ce8436a7 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=377b71db585c9c705f8e > > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=139a6bb0580000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16974a4c580000 > > > > > > Downloadable assets: > > > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-1a9239bb.raw.xz > > > vmlinux: https://storage.googleapis.com/syzbot-assets/bd56e2f824c3/vmlinux-1a9239bb.xz > > > kernel image: https://storage.googleapis.com/syzbot-assets/19172b7f9497/bzImage-1a9239bb.xz > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+377b71db585c9c705f8e@syzkaller.appspotmail.com > > > > > > ============================================ > > > WARNING: possible recursive locking detected > > > 6.14.0-syzkaller-05877-g1a9239bb4253 #0 Not tainted > > > -------------------------------------------- > > > dhcpcd/5649 is trying to acquire lock: > > > ffff888023ad4d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2751 [inline] > > > ffff888023ad4d28 (&dev->lock){+.+.}-{4:4}, at: netif_napi_add_weight include/linux/netdevice.h:2783 [inline] > > > ffff888023ad4d28 (&dev->lock){+.+.}-{4:4}, at: lapbeth_new_device drivers/net/wan/lapbether.c:415 [inline] > > > ffff888023ad4d28 (&dev->lock){+.+.}-{4:4}, at: lapbeth_device_event+0x586/0xbe0 drivers/net/wan/lapbether.c:460 > > > > > > but task is already holding lock: > > > ffff888029940d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2751 [inline] > > > ffff888029940d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline] > > > ffff888029940d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:39 [inline] > > > ffff888029940d28 (&dev->lock){+.+.}-{4:4}, at: dev_change_flags+0xa7/0x250 net/core/dev_api.c:67 > > > > > > other info that might help us debug this: > > > Possible unsafe locking scenario: > > > > > > CPU0 > > > ---- > > > lock(&dev->lock); > > > lock(&dev->lock); > > > > > > *** DEADLOCK *** > > > > > > May be due to missing lock nesting notation > > > > > > 2 locks held by dhcpcd/5649: > > > #0: ffffffff900fb268 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline] > > > #0: ffffffff900fb268 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x26d/0x1f50 net/ipv4/devinet.c:1121 > > > #1: ffff888029940d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2751 [inline] > > > #1: ffff888029940d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline] > > > #1: ffff888029940d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:39 [inline] > > > #1: ffff888029940d28 (&dev->lock){+.+.}-{4:4}, at: dev_change_flags+0xa7/0x250 net/core/dev_api.c:67 > > > > > > stack backtrace: > > > CPU: 1 UID: 0 PID: 5649 Comm: dhcpcd Not tainted 6.14.0-syzkaller-05877-g1a9239bb4253 #0 PREEMPT(full) > > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 > > > Call Trace: > > > > > > __dump_stack lib/dump_stack.c:94 [inline] > > > dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 > > > print_deadlock_bug+0x1e9/0x240 kernel/locking/lockdep.c:3042 > > > check_deadlock kernel/locking/lockdep.c:3094 [inline] > > > validate_chain kernel/locking/lockdep.c:3896 [inline] > > > __lock_acquire+0xff7/0x1ba0 kernel/locking/lockdep.c:5235 > > > lock_acquire kernel/locking/lockdep.c:5866 [inline] > > > lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823 > > > __mutex_lock_common kernel/locking/mutex.c:587 [inline] > > > __mutex_lock+0x19a/0xb00 kernel/locking/mutex.c:732 > > > netdev_lock include/linux/netdevice.h:2751 [inline] > > > netif_napi_add_weight include/linux/netdevice.h:2783 [inline] > > > lapbeth_new_device drivers/net/wan/lapbether.c:415 [inline] > > > lapbeth_device_event+0x586/0xbe0 drivers/net/wan/lapbether.c:460 > > > notifier_call_chain+0xb9/0x410 kernel/notifier.c:85 > > > call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2180 > > > call_netdevice_notifiers_extack net/core/dev.c:2218 [inline] > > > call_netdevice_notifiers net/core/dev.c:2232 [inline] > > > __dev_notify_flags+0x12c/0x2e0 net/core/dev.c:9409 > > > netif_change_flags+0x108/0x160 net/core/dev.c:9438 > > > dev_change_flags+0xba/0x250 net/core/dev_api.c:68 > > > devinet_ioctl+0x11d5/0x1f50 net/ipv4/devinet.c:1200 > > > inet_ioctl+0x3a7/0x3f0 net/ipv4/af_inet.c:1001 > > > sock_do_ioctl+0x115/0x280 net/socket.c:1190 > > > sock_ioctl+0x227/0x6b0 net/socket.c:1311 > > > vfs_ioctl fs/ioctl.c:51 [inline] > > > __do_sys_ioctl fs/ioctl.c:906 [inline] > > > __se_sys_ioctl fs/ioctl.c:892 [inline] > > > __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892 > > > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > > > do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94 > > > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > > RIP: 0033:0x7effd384cd49 > > > Code: 5c c3 48 8d 44 24 08 48 89 54 24 e0 48 89 44 24 c0 48 8d 44 24 d0 48 89 44 24 c8 b8 10 00 00 00 c7 44 24 b8 10 00 00 00 0f 05 <41> 89 c0 3d 00 f0 ff ff 76 10 48 8b 15 ae 60 0d 00 f7 d8 41 83 c8 > > > RSP: 002b:00007ffedd440088 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > > > RAX: ffffffffffffffda RBX: 00007effd377e6c0 RCX: 00007effd384cd49 > > > RDX: 00007ffedd450278 RSI: 0000000000008914 RDI: 000000000000001a > > > RBP: 00007ffedd460438 R08: 00007ffedd450238 R09: 00007ffedd4501e8 > > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > > > R13: 00007ffedd450278 R14: 0000000000000028 R15: 0000000000008914 > > > > > > > > > > > > --- > > > If you want syzbot to run the reproducer, reply with: > > > #syz test: git://repo/address.git branch-or-commit-hash > > > If you attach or paste a git patch, syzbot will apply it before testing. > > > > #syz test > > > > diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c > > index 56326f38fe8a..a022e930bd8e 100644 > > --- a/drivers/net/wan/lapbether.c > > +++ b/drivers/net/wan/lapbether.c > > @@ -39,6 +39,7 @@ > > #include > > #include > > > > +#include > > #include > > > > static const u8 bcast_addr[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }; > > @@ -372,6 +373,7 @@ static void lapbeth_setup(struct net_device *dev) > > dev->hard_header_len = 0; > > dev->mtu = 1000; > > dev->addr_len = 0; > > + netdev_lockdep_set_classes(netdev); > > } > > > > /* Setup a new device. > > > > I can resubmit https://lore.kernel.org/netdev/Z84MME6rwU6q9aJa@mini-arch/T/ Ah, this was not pulled because of net vs net-next? Yes, please do!