====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.8075/6285 is trying to acquire lock: ffffffff90094cc0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:316 [inline] ffffffff90094cc0 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages+0x149/0x5f0 mm/page_alloc.c:5118 but task is already holding lock: ffff88807d6c7180 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:619 [inline] ffff88807d6c7180 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:539 [inline] ffff88807d6c7180 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x36/0x340 mm/mmap_lock.c:599 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #7 (&mm->mmap_lock){++++}-{4:4}: __might_fault+0xcb/0x130 mm/memory.c:7530 _inline_copy_from_user include/linux/uaccess.h:169 [inline] _copy_from_user+0x28/0xb0 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:7628 [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+0x210/0x2000 net/core/skbuff.c:7640 ip_generic_getfrag+0x149/0x2d0 net/ipv4/ip_output.c:949 __ip6_append_data+0x3b26/0x40c0 net/ipv6/ip6_output.c:1736 ip6_append_data+0x108/0x270 net/ipv6/ip6_output.c:1891 rawv6_sendmsg+0x1298/0x18c0 net/ipv6/raw.c:916 sock_sendmsg_nosec+0x10f/0x190 net/socket.c:801 __sock_sendmsg net/socket.c:818 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2715 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2769 __sys_sendmsg net/socket.c:2801 [inline] __do_sys_sendmsg net/socket.c:2806 [inline] __se_sys_sendmsg net/socket.c:2804 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2804 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #6 (sk_lock-AF_INET6){+.+.}-{0:0}: lock_sock_nested+0x41/0x100 net/core/sock.c:3908 lock_sock include/net/sock.h:1717 [inline] inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:911 nbd_mark_nsock_dead+0x2cb/0x550 drivers/block/nbd.c:319 recv_work+0x1d14/0x1e30 drivers/block/nbd.c:1030 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 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:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x373/0xff0 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2131 __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+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x167/0x2f0 block/blk-mq.c:2546 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #4 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 nbd_queue_rq+0xc1/0xff0 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2131 __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+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x167/0x2f0 block/blk-mq.c:2546 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #3 (set->srcu){.+.+}-{0:0}: srcu_lock_sync include/linux/srcu.h:225 [inline] __synchronize_srcu+0xca/0x2f0 kernel/rcu/srcutree.c:1662 elevator_switch+0x1e8/0x7b0 block/elevator.c:576 elevator_change+0x2fa/0x480 block/elevator.c:681 elevator_set_default+0x375/0x440 block/elevator.c:754 blk_register_queue+0x404/0x4f0 block/blk-sysfs.c:992 __add_disk+0x6b8/0xdb0 block/genhd.c:531 add_disk_fwnode+0x100/0x3a0 block/genhd.c:600 add_disk include/linux/blkdev.h:801 [inline] nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2026 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743 do_one_initcall+0x250/0x870 init/main.c:1419 do_initcall_level+0x10a/0x1a0 init/main.c:1481 do_initcalls+0x59/0xa0 init/main.c:1497 kernel_init_freeable+0x29d/0x3e0 init/main.c:1732 kernel_init+0x22/0x1d0 init/main.c:1622 ret_from_fork+0x514/0xb70 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:646 [inline] __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821 elevator_change+0x1af/0x480 block/elevator.c:679 elevator_set_none+0xb5/0x140 block/elevator.c:769 blk_mq_elv_switch_none block/blk-mq.c:5114 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5159 [inline] blk_mq_update_nr_hw_queues+0x5ef/0x19e0 block/blk-mq.c:5224 nbd_start_device+0x189/0xb30 drivers/block/nbd.c:1530 nbd_genl_connect+0x167d/0x1cd0 drivers/block/nbd.c:2310 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2584 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline] netlink_unicast+0x8ef/0xa80 net/netlink/af_netlink.c:1361 netlink_sendmsg+0x7f0/0xb20 net/netlink/af_netlink.c:1920 sock_sendmsg_nosec+0x14e/0x190 net/socket.c:800 __sock_sendmsg net/socket.c:818 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2715 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2769 __sys_sendmsg net/socket.c:2801 [inline] __do_sys_sendmsg net/socket.c:2806 [inline] __se_sys_sendmsg net/socket.c:2804 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2804 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&q->q_usage_counter(io)#52){++++}-{0:0}: blk_alloc_queue+0x544/0x690 block/blk-core.c:505 blk_mq_alloc_queue block/blk-mq.c:4439 [inline] __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4486 nbd_dev_add+0x494/0xb60 drivers/block/nbd.c:1996 nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743 do_one_initcall+0x250/0x870 init/main.c:1419 do_initcall_level+0x10a/0x1a0 init/main.c:1481 do_initcalls+0x59/0xa0 init/main.c:1497 kernel_init_freeable+0x29d/0x3e0 init/main.c:1732 kernel_init+0x22/0x1d0 init/main.c:1622 ret_from_fork+0x514/0xb70 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:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __fs_reclaim_acquire mm/page_alloc.c:4360 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4374 might_alloc include/linux/sched/mm.h:316 [inline] prepare_alloc_pages+0x149/0x5f0 mm/page_alloc.c:5118 __alloc_frozen_pages_noprof+0x17c/0x410 mm/page_alloc.c:5429 alloc_pages_mpol+0x21e/0x390 mm/mempolicy.c:2511 alloc_frozen_pages_noprof mm/mempolicy.c:2582 [inline] alloc_pages_noprof+0xb1/0x2b0 mm/mempolicy.c:2602 pagetable_alloc_noprof include/linux/mm.h:3949 [inline] __pte_alloc_one_noprof include/asm-generic/pgalloc.h:76 [inline] pte_alloc_one+0x22/0x370 arch/x86/mm/pgtable.c:18 do_fault_around mm/memory.c:6021 [inline] do_read_fault mm/memory.c:6060 [inline] do_fault mm/memory.c:6203 [inline] do_pte_missing+0x1358/0x3570 mm/memory.c:4763 handle_pte_fault mm/memory.c:6627 [inline] __handle_mm_fault mm/memory.c:6776 [inline] handle_mm_fault+0x1a53/0x3750 mm/memory.c:6943 do_user_addr_fault+0x7f6/0x1480 arch/x86/mm/fault.c:1394 handle_page_fault arch/x86/mm/fault.c:1483 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595 user_access_begin arch/x86/include/asm/uaccess.h:466 [inline] copy_iovec_from_user lib/iov_iter.c:1293 [inline] __import_iovec_ubuf lib/iov_iter.c:1370 [inline] __import_iovec+0x1a4/0x7e0 lib/iov_iter.c:1389 import_iovec+0x73/0xa0 lib/iov_iter.c:1456 vfs_writev+0x1cf/0x990 fs/read_write.c:1043 do_writev+0x154/0x2e0 fs/read_write.c:1104 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 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: fs_reclaim --> sk_lock-AF_INET6 --> &mm->mmap_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&mm->mmap_lock); lock(sk_lock-AF_INET6); lock(&mm->mmap_lock); lock(fs_reclaim); *** DEADLOCK *** locks held by syz.3.8075/6285: 2, last CPU#0: #0: ffff888023ff70b0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x118/0x160 fs/file.c:1409 #1: ffff88807d6c7180 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:619 [inline] #1: ffff88807d6c7180 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:539 [inline] #1: ffff88807d6c7180 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x36/0x340 mm/mmap_lock.c:599 stack backtrace: CPU: 0 UID: 0 PID: 6285 Comm: syz.3.8075 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219 check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __fs_reclaim_acquire mm/page_alloc.c:4360 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4374 might_alloc include/linux/sched/mm.h:316 [inline] prepare_alloc_pages+0x149/0x5f0 mm/page_alloc.c:5118 __alloc_frozen_pages_noprof+0x17c/0x410 mm/page_alloc.c:5429 alloc_pages_mpol+0x21e/0x390 mm/mempolicy.c:2511 alloc_frozen_pages_noprof mm/mempolicy.c:2582 [inline] alloc_pages_noprof+0xb1/0x2b0 mm/mempolicy.c:2602 pagetable_alloc_noprof include/linux/mm.h:3949 [inline] __pte_alloc_one_noprof include/asm-generic/pgalloc.h:76 [inline] pte_alloc_one+0x22/0x370 arch/x86/mm/pgtable.c:18 do_fault_around mm/memory.c:6021 [inline] do_read_fault mm/memory.c:6060 [inline] do_fault mm/memory.c:6203 [inline] do_pte_missing+0x1358/0x3570 mm/memory.c:4763 handle_pte_fault mm/memory.c:6627 [inline] __handle_mm_fault mm/memory.c:6776 [inline] handle_mm_fault+0x1a53/0x3750 mm/memory.c:6943 do_user_addr_fault+0x7f6/0x1480 arch/x86/mm/fault.c:1394 handle_page_fault arch/x86/mm/fault.c:1483 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595 RIP: 0010:copy_iovec_from_user lib/iov_iter.c:1300 [inline] RIP: 0010:__import_iovec_ubuf lib/iov_iter.c:1370 [inline] RIP: 0010:__import_iovec+0x1a4/0x7e0 lib/iov_iter.c:1389 Code: 38 00 74 08 4c 89 f7 e8 6a 0d 54 fd 49 c7 06 00 00 00 00 4d 89 e6 e9 99 04 00 00 4d 39 e7 0f 82 2d 05 00 00 0f 01 cb 0f ae e8 <4d> 8b 6c 24 08 49 8b 1c 24 31 ff 4c 89 ee e8 89 34 dd fc 4d 85 ed RSP: 0018:ffffc90008bbfb50 EFLAGS: 00050206 RAX: ffffffff84ebe5ea RBX: 0000000000000008 RCX: ffff888033f13e80 RDX: 0000000000000002 RSI: 0000200000000100 RDI: 00007ffffffff000 RBP: 0000000000000001 R08: ffffc90008bbfd40 R09: ffffc90008bbfd60 R10: ffffc90008bbfd60 R11: fffff52001177fb1 R12: 0000200000000100 R13: 0000000000000000 R14: ffffc90008bbfca0 R15: 00007ffffffff000 import_iovec+0x73/0xa0 lib/iov_iter.c:1456 vfs_writev+0x1cf/0x990 fs/read_write.c:1043 do_writev+0x154/0x2e0 fs/read_write.c:1104 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f437f39fb19 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:00007f4380189028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: 00007f437f625fa0 RCX: 00007f437f39fb19 RDX: 0000000000000001 RSI: 0000200000000100 RDI: 0000000000000004 RBP: 00007f437f437b70 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f437f626038 R14: 00007f437f625fa0 R15: 00007ffee8143478 ---------------- Code disassembly (best guess): 0: 38 00 cmp %al,(%rax) 2: 74 08 je 0xc 4: 4c 89 f7 mov %r14,%rdi 7: e8 6a 0d 54 fd call 0xfd540d76 c: 49 c7 06 00 00 00 00 movq $0x0,(%r14) 13: 4d 89 e6 mov %r12,%r14 16: e9 99 04 00 00 jmp 0x4b4 1b: 4d 39 e7 cmp %r12,%r15 1e: 0f 82 2d 05 00 00 jb 0x551 24: 0f 01 cb stac 27: 0f ae e8 lfence * 2a: 4d 8b 6c 24 08 mov 0x8(%r12),%r13 <-- trapping instruction 2f: 49 8b 1c 24 mov (%r12),%rbx 33: 31 ff xor %edi,%edi 35: 4c 89 ee mov %r13,%rsi 38: e8 89 34 dd fc call 0xfcdd34c6 3d: 4d 85 ed test %r13,%r13