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h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Ovu38/2irAic1wC8D3hnyJaNPVBih/rjqfMQijEdReK/hl0sijpqTHij64OAkpuxC qUvDg4Rr1o50TzMIZvvYrwKd66qRcM/Qkf8vYiY/SMmeg/fLssxAn77cLcIWZKlHlc JutzY48ShA37FA5MDoFUvqyu/obhyNCm3G3ZuflIu+q1ohZhNhzeuspxgUOOpSEVkr nsGQ7S/qdzp6j4QmgsvlPyaN0rX8IEGlN3uLTbz/cLVs5Zc8/twpFh0dgt+G7jLrjm 4uceXBZS6YL6UGaLpHw7j9FIehRZF0r6KS9TlkuITAEHTjGu+FW4vexxDyvuuT/4Ug 4UeHudMK7foEg== Date: Sat, 14 Nov 2026 19:19:46 +0000 From: "Lorenzo Stoakes (ARM)" To: syzbot Cc: akpm@linux-foundation.org, jannh@google.com, liam@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pfalcato@suse.de, syzkaller-bugs@googlegroups.com, vbabka@kernel.org, Josef Bacik , Jens Axboe , linux-block@vger.kernel.org, nbd@other.debian.org Subject: Re: [syzbot] [mm?] possible deadlock in dup_mmap Message-ID: References: <6af85d8c.097d52ff.3d440.0008.GAE@google.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6af85d8c.097d52ff.3d440.0008.GAE@google.com> X-Stat-Signature: b77u4pxxyp9oy74h88hbfqkjhf1fo3uf X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CAD90A0002 X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794683993-793862 X-HE-Meta: U2FsdGVkX1/1o4Ip386gy4pS2eZtbgUIiNRJFzu9wXPQzhqq3QzqCjS+wSWUqRej3cm8qm/0VNyKVtom9XpcpHPPI6VCopkFnbOXbPX4is0egFDQrhy42Yw/E/10hpnTEEsPYstCWbTJHWUFYRluwjbxwDVH8nnaTkSDqKzIzydxo7GSBMI7LxZyUNt+FaD2FD7sh/L/c1WLiznOaGV5mbwywfUKya/nXgZdfzcsz2Xsw2E+jRqVCBYeJEL/X/2Ui4lHvLywzTGSY4FMl62QmcBTFWKPhdWCZFYyi2QQ64Ma82cZPyP8JGYDADd3akCVrnC75e+oO/+8ejmvcGiuHpmGn9OE04c/pVPGuViI1cZQrKgYe4hKtsSA6oDF4tEGqR0ngdorFJpQbi5s36UaEkLTrfaqBayJwnmMxMz8XVvNnRrp2punIG/WMeTZz2QtVhXGklXa99Jt5EPo1+Of8wTSz1LD23dJm21BdUbM6kYCK4yp36V+HbUbj91v60mAItP+4SvWUkLOzR35vwwHbHDlshJyucpn7MP57ajoNW3XTJvfZtuarVei8DOXjMV8f56PkiPGuLI8qMyP69C+xw8RHoQIEsHlEGk19PJ1DwVZ3eU0lj3ISFIDCwFTagVB7dmfZOBVKUXE89iUnuNfiPC7VFD6JPVqjYkcvf0jigjBtTI7pOv23ZW5PNOhelKK4zMFawp3J9xkylL3X/SDbynXRt43xxlDTridqil7MUIkSl98Yri9atyMIr1eTj5vJIyziEc1kyd/Tv7ddUQe7R7NoX7UEoNwHAY7aoTAlE9QK7WA0umyIZv67wmrXh1a7TzNWZrhF2Af//428XheDfF4SYK4n+FxOro8sKPijqKdp6Y0JlXhodvBfYq1d9LStoywmJweNQSCku6y5wevc5pMr46FnHOJ+n+5DlmolbgnmQinNh2K0vWRiYWNqPwkeIBwKnmCWsr8VUJOJYk Su3oGCHV 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 O8ij5pJE qHc/+qc1YPP0w1T/TQZOOvOXSOVN702oqNYxIEUCd4W4+xESuI0Mp9acjpeNQ8189kawsbVi36tLlsvokkGAWVG2smq37zTz6zK6ek49KPT4oXePOBgF6xMjur/dUTTy7WsUPY1qHfHVu8FdUtF0rOTL0T6Rz/W4ngVIHzQGS20= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 +cc block people + lists On Sat, Nov 14, 2026 at 05:09:32AM -0800, syzbot wrote: > 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. Hmm, AI identifies the nbd block driver but then only mm people are cc'd :)) Hey Jens, Josef :P > > 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 -- Cheers, Lorenzo