From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.210.72 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794661773; b=ZHuHdq96+j/PZRJ8Hx5gkhlPxqnAI12t5t/HafiL6wfuH5XX8kVmFuK02Bv/gWH1hzh+ ykmOy5OSToyasGJRhyCZFBodMd+nSPZBVDz8mwCX5aqKq9MxK6y+NH85UM5XWpoGJcOIc NDksSn/GUJLoPLapHJrfuzVYPzwOr5OVkTnBZYd4+YC5W9xWR6vDx6b4gWGVNvte/SJ+a o4Vn0uw1kkMz4uNB1tJyzfC8jzhjCPc/cHxoYIfFHkieJCnBhmuv61Du9oSMmEK1A7rWd G0HU3he0zq6GpWunNHMkZAB9b1XAMmSBcHd+RZ+HbYJ99y8eB+8X8S6q61u+sOyy79Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794661773; h=DMARC-Filter:Received:X-Google-DKIM-Signature:X-Forwarded-Encrypted: X-Gm-Message-State:MIME-Version:X-Received:Date: X-Google-Appengine-App-Id:X-Google-Appengine-App-Id-Alias:Message-ID: Subject:From:To:Content-Type; bh=yTGQ1aK3YK82hsq0r4vmh7QrXw/LxtQj96hfn8kq+8w=; b=sRL/gw3Fs/h6PP8E0ErGnAtQRyBvJ6SkT9u+fTkFeJKt8cjKV/juXicThFLEyQL39150 Ibql7n+yoQEvhImCh36ET1IFA74nuX/O81uNGaeJGzB+tgmD4leXdN6szlJVbSQX64mg1 IEMLUnpYAfQ6eHkZj8Kg9FzVBoFBaioXOYmONx9Fh1P4vyu4IPzOMe9nxFG+A+jzo9Znb bq61s+YJGwYsvmU6MezdHYiHqH80+7oXb/MrOpmCG2bU6FyO0WcabvDYzDb66L22oEp++ IY8YaT3oUVskMrQFKAG3qGRxf6YMafnVZIDK/sJtL37nVv0Ug8Sl5NYJXi/R/d4Sfmg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.remote-ip=209.85.210.72 Received: from mail-ot1-f72.google.com (mail-ot1-f72.google.com [209.85.210.72]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 414D5606E0C2 for ; Sat, 14 Nov 2026 13:09:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 414D5606E0C2 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-f72.google.com with SMTP id 46e09a7af769-851f720d7afso1065846a34.3 for ; Sat, 14 Nov 2026 05:09:33 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1794661772; x=1795266572; 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=yTGQ1aK3YK82hsq0r4vmh7QrXw/LxtQj96hfn8kq+8w=; b=C8PmSCoiOhsfFh3AeEDTqYuvscIdRuZI7MZLD5yNNSjQ15BBjmwdhCY5rSC/TBE3+X SMU/SM0ZLeyEHssb7Lcev4bToJeoc8ZR9BgR45gECOxkXz/zPouK1WZ7duyHso7yoOeA R/29ctQ2WNPPTqBRlidBPWQ1R2LxZ46owq8WiXuR5knmuJWu6UFNTjE6fpvr92wYWP2w CdPvTB+xUOXFhXLKL2h+UFgrwS7dC7yA8KONqTuX49ss/YDnT4wCHmlyXJvB/mhJ2JQ9 dKRShHC5e9oDZKBX+SlVGD8SyE1JA1DhC3YemfbT/gxIfLcBUG9qMf/bp4TXmJidY5BW XRkA== X-Forwarded-Encrypted: i=1; AL+hErEoy7WchsbZn61Wavgz626xHvZXK3zkVnFtgqahZ/ZHl1GICy7oSPdK9xNI8r4Cw1sdxq7bAjA9xVKmMBk=@vger.kernel.org X-Gm-Message-State: APuU4Z+IV8wCtY0iWqESHwMvBSkC1DXa+uS95NprhDWvdmuWt94+8vJX mnYwyQjXRpz6R/OozhoPaNnIzz1gAktLeF9fHwZx63Tzloe6mK/8Bp3th0zD4GwHdpbOF9mWgrG Zdx1rOC/y4PMhA/ka5bc39q/PsAvEjHnH77o+Pu5hxMqkZoYC5IE5o4ECMx0= X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-Received: by 2002:a05:6808:bc1:b0:4cb:ae51:5971 with SMTP id 5614622812f47-56e640d29f9mr4931195b6e.32.1794661772242; Sat, 14 Nov 2026 05:09:32 -0800 (PST) Date: Sat, 14 Nov 2026 05:09:32 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6af85d8c.097d52ff.3d440.0008.GAE@google.com> Subject: [syzbot] [mm?] possible deadlock in dup_mmap From: syzbot To: akpm@linux-foundation.org, jannh@google.com, liam@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, pfalcato@suse.de, syzkaller-bugs@googlegroups.com, vbabka@kernel.org Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 7e1392a42ea2 Merge tag 'net-7.4-rc3' of git://git.kernel.o.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10de62c3580000 kernel config: https://syzkaller.appspot.com/x/.config?x=e3d788a0111c0780 dashboard link: https://syzkaller.appspot.com/bug?extid=1cd3a506d57e74040004 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/cab3108790d1/disk-7e1392a4.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/d2cfcac3b02d/vmlinux-7e1392a4.xz kernel image: https://storage.googleapis.com/syzbot-assets/0b6b5a126605/bzImage-7e1392a4.xz AI-generated root cause summary: The circular locking dependency is rooted in drivers/block/nbd.c, where the Network Block Device driver handles block I/O under direct memory reclaim (fs_reclaim) using a network socket provided by userspace. In nbd_reclassify_socket(), NBD silently fails to reclassify the socket's lockdep class when sock_allow_reclassification() returns false (e.g., if the socket is already in use by userspace), leaving it in the generic sk_lock-AF_INET6 class. Furthermore, because userspace retains the socket descriptor, concurrent user operations like sendmsg() acquire lock_sock before faulting on user buffers (which acquires mm->mmap_lock), while NBD I/O and shutdown paths (e.g., nbd_mark_nsock_dead()) acquire lock_sock via kernel_sock_shutdown() under nsock->tx_lock in the fs_reclaim path. Because MM operations (such as fork/dup_mmap) take mm->mmap_lock and hugetlbfs_i_mmap_rwsem_key prior to GFP_KERNEL allocations (fs_reclaim), this establishes an inverted cycle: mm->mmap_lock -> hugetlbfs_i_mmap_rwsem_key -> fs_reclaim -> nsock->tx_lock -> sk_lock -> mm->mmap_lock. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=1cd3a506d57e74040004 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+1cd3a506d57e74040004@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.9.7569/29103 is trying to acquire lock: ffff888052efb930 (&hugetlbfs_i_mmap_rwsem_key){+.+.}-{4:4}, at: i_mmap_lock_write include/linux/fs.h:508 [inline] ffff888052efb930 (&hugetlbfs_i_mmap_rwsem_key){+.+.}-{4:4}, at: dup_mmap+0xb09/0x2180 mm/mmap.c:1802 but task is already holding lock: ffff88807fe0e540 (&mm->mmap_lock/1){+.+.}-{4:4}, at: mmap_write_lock_nested include/linux/mmap_lock.h:556 [inline] ffff88807fe0e540 (&mm->mmap_lock/1){+.+.}-{4:4}, at: dup_mmap+0x16e/0x2180 mm/mmap.c:1722 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #9 (&mm->mmap_lock/1){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 down_write_nested+0x8f/0x1f0 kernel/locking/rwsem.c:1757 mmap_write_lock_nested include/linux/mmap_lock.h:556 [inline] dup_mmap+0x16e/0x2180 mm/mmap.c:1722 dup_mm kernel/fork.c:1549 [inline] copy_mm kernel/fork.c:1602 [inline] copy_process+0x7c5c/0x88e0 kernel/fork.c:2328 kernel_clone+0x176/0x9d0 kernel/fork.c:2798 __do_sys_clone+0xd9/0x120 kernel/fork.c:2940 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #8 (&mm->mmap_lock){++++}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __might_fault+0xde/0x140 mm/memory.c:7575 _inline_copy_from_user include/linux/uaccess.h:169 [inline] _copy_from_user+0x29/0xd0 lib/usercopy.c:18 copy_from_user include/linux/uaccess.h:222 [inline] csum_and_copy_from_user include/net/checksum.h:31 [inline] copy_from_user_iter_csum net/core/skbuff.c:7677 [inline] iterate_ubuf include/linux/iov_iter.h:30 [inline] iterate_and_advance2 include/linux/iov_iter.h:302 [inline] csum_and_copy_from_iter_full+0x21a/0x1fe0 net/core/skbuff.c:7689 ip_generic_getfrag+0x172/0x270 net/ipv4/ip_output.c:949 raw6_getfrag+0x22c/0x290 net/ipv6/raw.c:743 __ip6_append_data+0x37f0/0x4b30 net/ipv6/ip6_output.c:1739 ip6_append_data net/ipv6/ip6_output.c:1894 [inline] ip6_append_data+0x10b/0x410 net/ipv6/ip6_output.c:1863 rawv6_sendmsg+0x169c/0x4630 net/ipv6/raw.c:917 inet_sendmsg+0x11c/0x140 net/ipv4/af_inet.c:866 sock_sendmsg_nosec net/socket.c:800 [inline] __sock_sendmsg net/socket.c:818 [inline] ____sys_sendmsg+0x9a0/0xb90 net/socket.c:2713 ___sys_sendmsg+0x208/0x270 net/socket.c:2770 __sys_sendmsg+0x160/0x210 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #7 (sk_lock-AF_INET6){+.+.}-{0:0}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 lock_sock_nested+0x41/0xf0 net/core/sock.c:3906 lock_sock include/net/sock.h:1717 [inline] inet_shutdown+0x67/0x410 net/ipv4/af_inet.c:913 nbd_mark_nsock_dead+0xae/0x5c0 drivers/block/nbd.c:319 sock_shutdown+0x16b/0x200 drivers/block/nbd.c:420 nbd_clear_sock drivers/block/nbd.c:1463 [inline] nbd_config_put+0x3d5/0x9b0 drivers/block/nbd.c:1492 nbd_genl_connect+0xd72/0x1770 drivers/block/nbd.c:2319 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:2585 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1336 [inline] netlink_unicast+0x668/0x950 net/netlink/af_netlink.c:1362 netlink_sendmsg+0x9ac/0x10c0 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:800 [inline] __sock_sendmsg net/socket.c:818 [inline] ____sys_sendmsg+0xa13/0xb90 net/socket.c:2713 ___sys_sendmsg+0x208/0x270 net/socket.c:2770 __sys_sendmsg+0x160/0x210 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #6 (&nsock->tx_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x42d/0xfa0 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x428/0x1e60 block/blk-mq.c:2141 __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_work_fn+0x130/0x380 block/blk-mq.c:2555 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495 process_scheduled_works kernel/workqueue.c:3578 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659 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 -> #5 (&cmd->lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821 nbd_queue_rq+0xba/0xfa0 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x428/0x1e60 block/blk-mq.c:2141 __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_work_fn+0x130/0x380 block/blk-mq.c:2555 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495 process_scheduled_works kernel/workqueue.c:3578 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659 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 -> #4 (set->srcu){.+.+}-{0:0}: lock_sync kernel/locking/lockdep.c:5991 [inline] lock_sync+0xb5/0x120 kernel/locking/lockdep.c:5979 srcu_lock_sync include/linux/srcu.h:261 [inline] __synchronize_srcu+0xa2/0x310 kernel/rcu/srcutree.c:1662 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+0x49e/0x640 block/blk-sysfs.c:992 __add_disk+0x7dd/0xf10 block/genhd.c:531 add_disk_fwnode+0x118/0x480 block/genhd.c:600 add_disk include/linux/blkdev.h:799 [inline] nbd_dev_add+0x779/0xb10 drivers/block/nbd.c:2026 nbd_init+0x2c5/0x2e0 drivers/block/nbd.c:2743 do_one_initcall+0x11c/0x6f0 init/main.c:1419 do_initcall_level init/main.c:1481 [inline] do_initcalls init/main.c:1497 [inline] do_basic_setup init/main.c:1517 [inline] kernel_init_freeable+0x6ea/0x7b0 init/main.c:1732 kernel_init+0x21/0x1e0 init/main.c:1622 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #3 (&q->elevator_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821 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:5168 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5213 [inline] blk_mq_update_nr_hw_queues+0x4e1/0x1690 block/blk-mq.c:5281 nbd_start_device+0x1a6/0xbd0 drivers/block/nbd.c:1530 nbd_genl_connect+0xfc2/0x1770 drivers/block/nbd.c:2310 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:2585 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1336 [inline] netlink_unicast+0x668/0x950 net/netlink/af_netlink.c:1362 netlink_sendmsg+0x9ac/0x10c0 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:800 [inline] __sock_sendmsg net/socket.c:818 [inline] ____sys_sendmsg+0xa13/0xb90 net/socket.c:2713 ___sys_sendmsg+0x208/0x270 net/socket.c:2770 __sys_sendmsg+0x160/0x210 net/socket.c:2802 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (&q->q_usage_counter(io)#49){++++}-{0:0}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 blk_alloc_queue+0x610/0x790 block/blk-core.c:505 blk_mq_alloc_queue+0x174/0x290 block/blk-mq.c:4468 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4515 nbd_dev_add+0x491/0xb10 drivers/block/nbd.c:1996 nbd_init+0x2c5/0x2e0 drivers/block/nbd.c:2743 do_one_initcall+0x11c/0x6f0 init/main.c:1419 do_initcall_level init/main.c:1481 [inline] do_initcalls init/main.c:1497 [inline] do_basic_setup init/main.c:1517 [inline] kernel_init_freeable+0x6ea/0x7b0 init/main.c:1732 kernel_init+0x21/0x1e0 init/main.c:1622 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 (fs_reclaim){+.+.}-{0:0}: lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 __fs_reclaim_acquire mm/page_alloc.c:4375 [inline] fs_reclaim_acquire+0xc4/0x100 mm/page_alloc.c:4389 might_alloc include/linux/sched/mm.h:316 [inline] slab_pre_alloc_hook mm/slub.c:4673 [inline] slab_alloc_node mm/slub.c:5011 [inline] __kmalloc_cache_noprof+0x63/0x6d0 mm/slub.c:5676 _kmalloc_noprof include/linux/slab.h:991 [inline] allocate_file_region_entries+0x1a0/0x630 mm/hugetlb.c:711 region_chg+0x85/0x140 mm/hugetlb.c:831 __vma_reservation_common+0x34b/0x6f0 mm/hugetlb.c:2495 vma_needs_reservation mm/hugetlb.c:2562 [inline] hugetlb_unmap_range+0x10be/0x1710 mm/hugetlb.c:5415 __unmap_hugepage_range+0x186/0x2f0 mm/hugetlb.c:5445 __zap_vma_range+0x3870/0x46c0 mm/memory.c:2195 unmap_vmas+0x294/0x5f0 mm/memory.c:2275 exit_mmap+0x1ef/0xa40 mm/mmap.c:1315 __mmput+0x12a/0x410 kernel/fork.c:1192 mmput+0x62/0x70 kernel/fork.c:1215 exit_mm kernel/exit.c:586 [inline] do_exit+0x80c/0x2a00 kernel/exit.c:967 do_group_exit+0xd5/0x2a0 kernel/exit.c:1123 get_signal+0x1f58/0x22e0 kernel/signal.c:3113 arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline] exit_to_user_mode_loop+0x139/0x700 kernel/entry/common.c:101 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline] do_syscall_64+0x661/0x7b0 arch/x86/entry/syscall_64.c:107 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&hugetlbfs_i_mmap_rwsem_key){+.+.}-{4:4}: 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 down_write+0x86/0x1f0 kernel/locking/rwsem.c:1631 i_mmap_lock_write include/linux/fs.h:508 [inline] dup_mmap+0xb09/0x2180 mm/mmap.c:1802 dup_mm kernel/fork.c:1549 [inline] copy_mm kernel/fork.c:1602 [inline] copy_process+0x7c5c/0x88e0 kernel/fork.c:2328 kernel_clone+0x176/0x9d0 kernel/fork.c:2798 __do_sys_clone+0xd9/0x120 kernel/fork.c:2940 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &hugetlbfs_i_mmap_rwsem_key --> &mm->mmap_lock --> &mm->mmap_lock/1 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&mm->mmap_lock/1); lock(&mm->mmap_lock); lock(&mm->mmap_lock/1); lock(&hugetlbfs_i_mmap_rwsem_key); *** DEADLOCK *** locks held by syz.9.7569/29103: 3, on CPU#1: #0: ffffffff9014abf0 (dup_mmap_sem){++++}-{0:0}, at: dup_mm kernel/fork.c:1536 [inline] #0: ffffffff9014abf0 (dup_mmap_sem){++++}-{0:0}, at: copy_mm kernel/fork.c:1602 [inline] #0: ffffffff9014abf0 (dup_mmap_sem){++++}-{0:0}, at: copy_process+0x7b73/0x88e0 kernel/fork.c:2328 #1: ffff88807fe0ccc0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:566 [inline] #1: ffff88807fe0ccc0 (&mm->mmap_lock){++++}-{4:4}, at: dup_mm kernel/fork.c:1537 [inline] #1: ffff88807fe0ccc0 (&mm->mmap_lock){++++}-{4:4}, at: copy_mm kernel/fork.c:1602 [inline] #1: ffff88807fe0ccc0 (&mm->mmap_lock){++++}-{4:4}, at: copy_process+0x7b99/0x88e0 kernel/fork.c:2328 #2: ffff88807fe0e540 (&mm->mmap_lock/1){+.+.}-{4:4}, at: mmap_write_lock_nested include/linux/mmap_lock.h:556 [inline] #2: ffff88807fe0e540 (&mm->mmap_lock/1){+.+.}-{4:4}, at: dup_mmap+0x16e/0x2180 mm/mmap.c:1722 stack backtrace: CPU: 1 UID: 0 PID: 29103 Comm: syz.9.7569 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 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 down_write+0x86/0x1f0 kernel/locking/rwsem.c:1631 i_mmap_lock_write include/linux/fs.h:508 [inline] dup_mmap+0xb09/0x2180 mm/mmap.c:1802 dup_mm kernel/fork.c:1549 [inline] copy_mm kernel/fork.c:1602 [inline] copy_process+0x7c5c/0x88e0 kernel/fork.c:2328 kernel_clone+0x176/0x9d0 kernel/fork.c:2798 __do_sys_clone+0xd9/0x120 kernel/fork.c:2940 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f421cfa94d9 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:00007f421de4afd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038 RAX: ffffffffffffffda RBX: 00007f421d225fa0 RCX: 00007f421cfa94d9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000002820000 RBP: 00007f421d03804e R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 R13: 00007f421d226038 R14: 00007f421d225fa0 R15: 00007ffe923e2998 --- 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