From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D55D86BFCE; Mon, 13 Apr 2026 14:26:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776090404; cv=none; b=bUJywonZY0ptnJlfLsoO/53BJhAZukhQMAwA3jYVuUxQsRQJfWuJ/3xVqJt9eVh+6e/psb6EPCOg+4Y8CVet2ylhUK1gQRpWgWQ6dmsb3b/IXR9y6uPdoryGlUqUgn59ac7w6aDCVJp6c78O1rK7G/vUvlrMwJG97n4scQqXIPY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776090404; c=relaxed/simple; bh=1MZND6bJkp684teTokHALQaNO0jbgoKDXwoMO9NTZKs=; h=Message-ID:Date:MIME-Version:Subject:To:References:From:Cc: In-Reply-To:Content-Type; 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kCE7luIvyqMQ0DY13PXyMI1L0QdOkjv0JrmIIAPfWWJ/qWtuXw4sDMDosXkl5G+1x0 Rge8BgNRK1ihU/C6JbFRjJnfaWu9pWXljw75PcrB/DC0lYjHXI7kCV69297M/W8FRI 2Xqjy70+mMilQ== Message-ID: Date: Mon, 13 Apr 2026 16:26:38 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [syzbot] [mptcp?] possible deadlock in mptcp_pm_nl_set_flags Content-Language: fr To: syzbot References: <69d90c16.050a0220.adfb3.000a.GAE@google.com> From: Matthieu Baerts Cc: davem@davemloft.net, edumazet@google.com, geliang@kernel.org, horms@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, martineau@kernel.org, mptcp@lists.linux.dev, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Autocrypt: addr=matttbe@kernel.org; keydata= xsFNBFXj+ekBEADxVr99p2guPcqHFeI/JcFxls6KibzyZD5TQTyfuYlzEp7C7A9swoK5iCvf YBNdx5Xl74NLSgx6y/1NiMQGuKeu+2BmtnkiGxBNanfXcnl4L4Lzz+iXBvvbtCbynnnqDDqU 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Core In-Reply-To: <69d90c16.050a0220.adfb3.000a.GAE@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hello, On 10/04/2026 16:41, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 591cd656a1bf Linux 7.0-rc7 > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1779ce06580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=5a3e5e8c17cc174e > dashboard link: https://syzkaller.appspot.com/bug?extid=dfa28bb6444d8f169cbb > 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 (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-591cd656.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/3e99d0e29df0/vmlinux-591cd656.xz > kernel image: https://storage.googleapis.com/syzbot-assets/5877fee0a056/bzImage-591cd656.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+dfa28bb6444d8f169cbb@syzkaller.appspotmail.com > > netlink: 8 bytes leftover after parsing attributes in process `syz.8.6915'. > netlink: 8 bytes leftover after parsing attributes in process `syz.8.6915'. > ====================================================== > WARNING: possible circular locking dependency detected > syzkaller #0 Tainted: G L > ------------------------------------------------------ > syz.8.6915/29783 is trying to acquire lock: > ffffffff8e9ab8a0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline] > ffffffff8e9ab8a0 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4489 [inline] > ffffffff8e9ab8a0 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4843 [inline] > ffffffff8e9ab8a0 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_lru_noprof+0x51/0x6e0 mm/slub.c:4885 > > but task is already holding lock: > ffff888034761ae0 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1709 [inline] > ffff888034761ae0 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_pm_nl_set_flags_all net/mptcp/pm_kernel.c:1482 [inline] > ffff888034761ae0 (sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_pm_nl_set_flags+0x605/0xd30 net/mptcp/pm_kernel.c:1551 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #6 (sk_lock-AF_INET){+.+.}-{0:0}: > lock_sock_nested+0x41/0xf0 net/core/sock.c:3780 > lock_sock include/net/sock.h:1709 [inline] > inet_shutdown+0x67/0x410 net/ipv4/af_inet.c:919 > nbd_mark_nsock_dead+0xae/0x5c0 drivers/block/nbd.c:318 > recv_work+0x5fb/0x8c0 drivers/block/nbd.c:1021 > process_one_work+0xa23/0x19a0 kernel/workqueue.c:3276 > process_scheduled_works kernel/workqueue.c:3359 [inline] > worker_thread+0x5ef/0xe50 kernel/workqueue.c:3440 > kthread+0x370/0x450 kernel/kthread.c:436 > ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 > > -> #5 (&nsock->tx_lock){+.+.}-{4:4}: > __mutex_lock_common kernel/locking/mutex.c:614 [inline] > __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 > nbd_handle_cmd drivers/block/nbd.c:1143 [inline] > nbd_queue_rq+0x428/0x1080 drivers/block/nbd.c:1207 > blk_mq_dispatch_rq_list+0x422/0x1e70 block/blk-mq.c:2148 > __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] > blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] > __blk_mq_sched_dispatch_requests+0xcea/0x1620 block/blk-mq-sched.c:307 > blk_mq_sched_dispatch_requests+0xd7/0x1c0 block/blk-mq-sched.c:329 > blk_mq_run_hw_queue+0x23c/0x670 block/blk-mq.c:2386 > blk_mq_dispatch_list+0x51d/0x1360 block/blk-mq.c:2949 > blk_mq_flush_plug_list block/blk-mq.c:2997 [inline] > blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2969 > __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1230 > blk_finish_plug block/blk-core.c:1257 [inline] > __submit_bio+0x584/0x6c0 block/blk-core.c:649 > __submit_bio_noacct_mq block/blk-core.c:722 [inline] > submit_bio_noacct_nocheck+0x562/0xc10 block/blk-core.c:753 > submit_bio_noacct+0xd17/0x2010 block/blk-core.c:884 > blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline] > submit_bh_wbc+0x59c/0x770 fs/buffer.c:2821 > submit_bh fs/buffer.c:2826 [inline] > block_read_full_folio+0x4c8/0x8e0 fs/buffer.c:2458 > filemap_read_folio+0xfc/0x3b0 mm/filemap.c:2501 > do_read_cache_folio+0x2d7/0x6b0 mm/filemap.c:4101 > read_mapping_folio include/linux/pagemap.h:1017 [inline] > read_part_sector+0xd1/0x370 block/partitions/core.c:723 > adfspart_check_ICS+0x93/0x910 block/partitions/acorn.c:360 > check_partition block/partitions/core.c:142 [inline] > blk_add_partitions block/partitions/core.c:590 [inline] > bdev_disk_changed+0x7f8/0xc80 block/partitions/core.c:694 > blkdev_get_whole+0x187/0x290 block/bdev.c:764 > bdev_open+0x2c7/0xe40 block/bdev.c:973 > blkdev_open+0x34e/0x4f0 block/fops.c:697 > do_dentry_open+0x6d8/0x1660 fs/open.c:949 > vfs_open+0x82/0x3f0 fs/open.c:1081 > do_open fs/namei.c:4677 [inline] > path_openat+0x208c/0x31a0 fs/namei.c:4836 > do_file_open+0x20e/0x430 fs/namei.c:4865 > do_sys_openat2+0x10d/0x1e0 fs/open.c:1366 > do_sys_open fs/open.c:1372 [inline] > __do_sys_openat fs/open.c:1388 [inline] > __se_sys_openat fs/open.c:1383 [inline] > __x64_sys_openat+0x12d/0x210 fs/open.c:1383 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > -> #4 (&cmd->lock){+.+.}-{4:4}: > __mutex_lock_common kernel/locking/mutex.c:614 [inline] > __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 > nbd_queue_rq+0xba/0x1080 drivers/block/nbd.c:1199 > blk_mq_dispatch_rq_list+0x422/0x1e70 block/blk-mq.c:2148 > __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] > blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] > __blk_mq_sched_dispatch_requests+0xcea/0x1620 block/blk-mq-sched.c:307 > blk_mq_sched_dispatch_requests+0xd7/0x1c0 block/blk-mq-sched.c:329 > blk_mq_run_hw_queue+0x23c/0x670 block/blk-mq.c:2386 > blk_mq_dispatch_list+0x51d/0x1360 block/blk-mq.c:2949 > blk_mq_flush_plug_list block/blk-mq.c:2997 [inline] > blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2969 > __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1230 > blk_finish_plug block/blk-core.c:1257 [inline] > __submit_bio+0x584/0x6c0 block/blk-core.c:649 > __submit_bio_noacct_mq block/blk-core.c:722 [inline] > submit_bio_noacct_nocheck+0x562/0xc10 block/blk-core.c:753 > submit_bio_noacct+0xd17/0x2010 block/blk-core.c:884 > blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline] > submit_bh_wbc+0x59c/0x770 fs/buffer.c:2821 > submit_bh fs/buffer.c:2826 [inline] > block_read_full_folio+0x4c8/0x8e0 fs/buffer.c:2458 > filemap_read_folio+0xfc/0x3b0 mm/filemap.c:2501 > do_read_cache_folio+0x2d7/0x6b0 mm/filemap.c:4101 > read_mapping_folio include/linux/pagemap.h:1017 [inline] > read_part_sector+0xd1/0x370 block/partitions/core.c:723 > adfspart_check_ICS+0x93/0x910 block/partitions/acorn.c:360 > check_partition block/partitions/core.c:142 [inline] > blk_add_partitions block/partitions/core.c:590 [inline] > bdev_disk_changed+0x7f8/0xc80 block/partitions/core.c:694 > blkdev_get_whole+0x187/0x290 block/bdev.c:764 > bdev_open+0x2c7/0xe40 block/bdev.c:973 > blkdev_open+0x34e/0x4f0 block/fops.c:697 > do_dentry_open+0x6d8/0x1660 fs/open.c:949 > vfs_open+0x82/0x3f0 fs/open.c:1081 > do_open fs/namei.c:4677 [inline] > path_openat+0x208c/0x31a0 fs/namei.c:4836 > do_file_open+0x20e/0x430 fs/namei.c:4865 > do_sys_openat2+0x10d/0x1e0 fs/open.c:1366 > do_sys_open fs/open.c:1372 [inline] > __do_sys_openat fs/open.c:1388 [inline] > __se_sys_openat fs/open.c:1383 [inline] > __x64_sys_openat+0x12d/0x210 fs/open.c:1383 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > -> #3 (set->srcu){.+.+}-{0:0}: > srcu_lock_sync include/linux/srcu.h:199 [inline] > __synchronize_srcu+0xa2/0x300 kernel/rcu/srcutree.c:1481 > blk_mq_wait_quiesce_done block/blk-mq.c:284 [inline] > blk_mq_wait_quiesce_done block/blk-mq.c:281 [inline] > blk_mq_quiesce_queue block/blk-mq.c:304 [inline] > blk_mq_quiesce_queue+0x149/0x1c0 block/blk-mq.c:299 > elevator_switch+0x17b/0x7e0 block/elevator.c:576 > elevator_change+0x352/0x530 block/elevator.c:681 > elevator_set_default+0x29e/0x360 block/elevator.c:754 > blk_register_queue+0x412/0x590 block/blk-sysfs.c:946 > __add_disk+0x73f/0xe40 block/genhd.c:528 > add_disk_fwnode+0x118/0x5c0 block/genhd.c:597 > add_disk include/linux/blkdev.h:785 [inline] > nbd_dev_add+0x77a/0xb10 drivers/block/nbd.c:1984 > nbd_init+0x291/0x2b0 drivers/block/nbd.c:2692 > do_one_initcall+0x11d/0x760 init/main.c:1382 > do_initcall_level init/main.c:1444 [inline] > do_initcalls init/main.c:1460 [inline] > do_basic_setup init/main.c:1479 [inline] > kernel_init_freeable+0x6e5/0x7a0 init/main.c:1692 > kernel_init+0x1f/0x1e0 init/main.c:1582 > ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 > > -> #2 (&q->elevator_lock){+.+.}-{4:4}: > __mutex_lock_common kernel/locking/mutex.c:614 [inline] > __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776 > elevator_change+0x1bc/0x530 block/elevator.c:679 > elevator_set_none+0x92/0xf0 block/elevator.c:769 > blk_mq_elv_switch_none block/blk-mq.c:5110 [inline] > __blk_mq_update_nr_hw_queues block/blk-mq.c:5155 [inline] > blk_mq_update_nr_hw_queues+0x4c1/0x15f0 block/blk-mq.c:5220 > nbd_start_device+0x1a6/0xbd0 drivers/block/nbd.c:1489 > nbd_genl_connect+0xff2/0x1a40 drivers/block/nbd.c:2239 > genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114 > genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] > genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209 > netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550 > genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 > netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] > netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344 > netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894 > sock_sendmsg_nosec net/socket.c:727 [inline] > __sock_sendmsg net/socket.c:742 [inline] > ____sys_sendmsg+0x9e1/0xb70 net/socket.c:2592 > ___sys_sendmsg+0x190/0x1e0 net/socket.c:2646 > __sys_sendmsg+0x170/0x220 net/socket.c:2678 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > -> #1 (&q->q_usage_counter(io)#51){++++}-{0:0}: > blk_alloc_queue+0x610/0x790 block/blk-core.c:461 > blk_mq_alloc_queue+0x174/0x290 block/blk-mq.c:4429 > __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4476 > nbd_dev_add+0x492/0xb10 drivers/block/nbd.c:1954 > nbd_init+0x291/0x2b0 drivers/block/nbd.c:2692 > do_one_initcall+0x11d/0x760 init/main.c:1382 > do_initcall_level init/main.c:1444 [inline] > do_initcalls init/main.c:1460 [inline] > do_basic_setup init/main.c:1479 [inline] > kernel_init_freeable+0x6e5/0x7a0 init/main.c:1692 > kernel_init+0x1f/0x1e0 init/main.c:1582 > ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 > > -> #0 (fs_reclaim){+.+.}-{0:0}: > check_prev_add kernel/locking/lockdep.c:3165 [inline] > check_prevs_add kernel/locking/lockdep.c:3284 [inline] > validate_chain kernel/locking/lockdep.c:3908 [inline] > __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 > lock_acquire kernel/locking/lockdep.c:5868 [inline] > lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825 > __fs_reclaim_acquire mm/page_alloc.c:4348 [inline] > fs_reclaim_acquire+0xc4/0x100 mm/page_alloc.c:4362 > might_alloc include/linux/sched/mm.h:317 [inline] > slab_pre_alloc_hook mm/slub.c:4489 [inline] > slab_alloc_node mm/slub.c:4843 [inline] > kmem_cache_alloc_lru_noprof+0x51/0x6e0 mm/slub.c:4885 > sock_alloc_inode+0x25/0x1c0 net/socket.c:322 > alloc_inode+0x68/0x250 fs/inode.c:347 > new_inode_pseudo include/linux/fs.h:3003 [inline] > sock_alloc+0x44/0x280 net/socket.c:637 > __sock_create+0xc2/0x860 net/socket.c:1569 > mptcp_subflow_create_socket+0xec/0xa30 net/mptcp/subflow.c:1790 > __mptcp_subflow_connect+0x3c6/0x1480 net/mptcp/subflow.c:1631 > mptcp_pm_create_subflow_or_signal_addr+0xc3e/0x18d0 net/mptcp/pm_kernel.c:416 > mptcp_pm_nl_fullmesh net/mptcp/pm_kernel.c:1460 [inline] > mptcp_pm_nl_set_flags_all net/mptcp/pm_kernel.c:1487 [inline] > mptcp_pm_nl_set_flags+0x814/0xd30 net/mptcp/pm_kernel.c:1551 > mptcp_pm_set_flags net/mptcp/pm_netlink.c:277 [inline] > mptcp_pm_nl_set_flags_doit+0x1b0/0x290 net/mptcp/pm_netlink.c:282 > genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114 > genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] > genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209 > netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550 > genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 > netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] > netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344 > netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894 > sock_sendmsg_nosec net/socket.c:727 [inline] > __sock_sendmsg net/socket.c:742 [inline] > ____sys_sendmsg+0x9e1/0xb70 net/socket.c:2592 > ___sys_sendmsg+0x190/0x1e0 net/socket.c:2646 > __sys_sendmsg+0x170/0x220 net/socket.c:2678 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > other info that might help us debug this: > > Chain exists of: > fs_reclaim --> &nsock->tx_lock --> sk_lock-AF_INET > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(sk_lock-AF_INET); > lock(&nsock->tx_lock); > lock(sk_lock-AF_INET); > lock(fs_reclaim); > > *** DEADLOCK *** Same here, if I'm not mistaken, it looks like this issue is also due to nbd introducing a lockdep dependency between reclaim and af_socket, and this is similar to a previous report: #syz dup: [syzbot] [mptcp?] possible deadlock in mptcp_subflow_create_socket (2) If that's not correct, please induplicate it. I'm not sure how MPTCP is being involved here, I guess it should not and a simple fix is to forbid it. But maybe this issue is not specific to MPTCP? Cheers, Matt -- Sponsored by the NGI0 Core fund.