====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ udevd/22142 is trying to acquire lock: ffffffff8ec848a0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline] ffffffff8ec848a0 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages+0x15b/0x650 mm/page_alloc.c:5048 but task is already holding lock: ffff888053b54378 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:611 [inline] ffff888053b54378 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:441 [inline] ffff888053b54378 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x36/0x340 mm/mmap_lock.c:501 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #8 (&mm->mmap_lock){++++}-{4:4}: __might_fault+0xcb/0x130 mm/memory.c:7292 _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:7451 [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+0x210/0x1fb0 net/core/skbuff.c:7463 ip_generic_getfrag+0x149/0x2d0 net/ipv4/ip_output.c:941 __ip6_append_data+0x3b26/0x40c0 net/ipv6/ip6_output.c:1732 ip6_append_data+0x108/0x270 net/ipv6/ip6_output.c:1887 rawv6_sendmsg+0x1298/0x18c0 net/ipv6/raw.c:913 sock_sendmsg_nosec+0x10e/0x180 net/socket.c:776 __sock_sendmsg net/socket.c:790 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2684 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2738 __sys_sendmsg net/socket.c:2770 [inline] __do_sys_sendmsg net/socket.c:2775 [inline] __se_sys_sendmsg net/socket.c:2773 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2773 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #7 (sk_lock-AF_INET6){+.+.}-{0:0}: lock_sock_nested+0x41/0x100 net/core/sock.c:3825 lock_sock include/net/sock.h:1713 [inline] tls_sw_sendmsg+0x161/0x2860 net/tls/tls_sw.c:1007 sock_sendmsg_nosec+0x90/0x180 net/socket.c:775 __sock_sendmsg net/socket.c:790 [inline] sock_write_iter+0x2de/0x3e0 net/socket.c:1241 do_iter_readv_writev+0x612/0x8c0 fs/read_write.c:-1 vfs_writev+0x343/0x990 fs/read_write.c:1058 do_writev+0x154/0x2e0 fs/read_write.c:1104 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #6 (&ctx->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 tls_sw_sendmsg+0x13c/0x2860 net/tls/tls_sw.c:1004 sock_sendmsg_nosec+0x90/0x180 net/socket.c:775 __sock_sendmsg net/socket.c:790 [inline] sock_sendmsg+0x1ca/0x2d0 net/socket.c:813 __sock_xmit+0x245/0x4f0 drivers/block/nbd.c:576 sock_xmit drivers/block/nbd.c:605 [inline] send_disconnects drivers/block/nbd.c:1443 [inline] nbd_disconnect+0x3ad/0x560 drivers/block/nbd.c:1458 nbd_disconnect_and_put+0x32/0x280 drivers/block/nbd.c:2294 nbd_genl_disconnect+0x4af/0x590 drivers/block/nbd.c:2340 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:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bb/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775 __sock_sendmsg net/socket.c:790 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2684 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2738 __sys_sendmsg net/socket.c:2770 [inline] __do_sys_sendmsg net/socket.c:2775 [inline] __se_sys_sendmsg net/socket.c:2773 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2773 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (&nsock->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x373/0x1150 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __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+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 kthread+0x388/0x470 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+0x19d/0x1550 kernel/locking/mutex.c:821 nbd_queue_rq+0xc1/0x1150 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2117 __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+0x16c/0x300 block/blk-mq.c:2532 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 kthread+0x388/0x470 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:199 [inline] __synchronize_srcu+0xc9/0x2f0 kernel/rcu/srcutree.c:1481 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+0x3f3/0x4e0 block/blk-sysfs.c:992 __add_disk+0x6cb/0xe30 block/genhd.c:528 add_disk_fwnode+0xfb/0x4b0 block/genhd.c:597 add_disk include/linux/blkdev.h:800 [inline] nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2021 nbd_init+0x15f/0x1e0 drivers/block/nbd.c:2729 do_one_initcall+0x250/0x870 init/main.c:1347 do_initcall_level+0x10a/0x1a0 init/main.c:1409 do_initcalls+0x59/0xa0 init/main.c:1425 kernel_init_freeable+0x29d/0x3e0 init/main.c:1658 kernel_init+0x1d/0x1d0 init/main.c:1548 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+0x19d/0x1550 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:5101 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5146 [inline] blk_mq_update_nr_hw_queues+0x5ef/0x19f0 block/blk-mq.c:5211 nbd_start_device+0x189/0xb30 drivers/block/nbd.c:1526 nbd_genl_connect+0x1597/0x1c10 drivers/block/nbd.c:2276 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:2556 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x7bb/0x940 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775 __sock_sendmsg net/socket.c:790 [inline] ____sys_sendmsg+0x54e/0x850 net/socket.c:2684 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2738 __sys_sendmsg net/socket.c:2770 [inline] __do_sys_sendmsg net/socket.c:2775 [inline] __se_sys_sendmsg net/socket.c:2773 [inline] __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2773 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&q->q_usage_counter(io)#49){++++}-{0:0}: blk_alloc_queue+0x544/0x690 block/blk-core.c:504 blk_mq_alloc_queue block/blk-mq.c:4420 [inline] __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4467 nbd_dev_add+0x494/0xb60 drivers/block/nbd.c:1991 nbd_init+0x15f/0x1e0 drivers/block/nbd.c:2729 do_one_initcall+0x250/0x870 init/main.c:1347 do_initcall_level+0x10a/0x1a0 init/main.c:1409 do_initcalls+0x59/0xa0 init/main.c:1425 kernel_init_freeable+0x29d/0x3e0 init/main.c:1658 kernel_init+0x1d/0x1d0 init/main.c:1548 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:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 __fs_reclaim_acquire mm/page_alloc.c:4329 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4343 might_alloc include/linux/sched/mm.h:317 [inline] prepare_alloc_pages+0x15b/0x650 mm/page_alloc.c:5048 __alloc_frozen_pages_noprof+0x12f/0x380 mm/page_alloc.c:5293 alloc_pages_mpol+0x212/0x380 mm/mempolicy.c:2490 folio_alloc_mpol_noprof+0x39/0x160 mm/mempolicy.c:2509 vma_alloc_folio_noprof+0xe1/0x1e0 mm/mempolicy.c:2544 folio_prealloc mm/memory.c:-1 [inline] wp_page_copy mm/memory.c:3875 [inline] do_wp_page+0x1163/0x4c70 mm/memory.c:4336 handle_pte_fault mm/memory.c:6395 [inline] __handle_mm_fault mm/memory.c:6517 [inline] handle_mm_fault+0x1490/0x3080 mm/memory.c:6686 do_user_addr_fault+0x744/0x1340 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 rep_movs_alternative+0x4a/0xa0 arch/x86/lib/copy_user_64.S:68 copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline] raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline] copy_to_user_iter lib/iov_iter.c:25 [inline] iterate_ubuf include/linux/iov_iter.h:30 [inline] iterate_and_advance2 include/linux/iov_iter.h:302 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] _copy_to_iter+0x255/0x1810 lib/iov_iter.c:197 copy_to_iter include/linux/uio.h:220 [inline] seq_read_iter+0xaae/0xca0 fs/seq_file.c:282 new_sync_read fs/read_write.c:493 [inline] vfs_read+0x595/0xa80 fs/read_write.c:574 ksys_read+0x150/0x270 fs/read_write.c:716 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 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 --> 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 *** 2 locks held by udevd/22142: #0: ffff8880570f2758 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xa4/0xca0 fs/seq_file.c:183 #1: ffff888053b54378 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:611 [inline] #1: ffff888053b54378 (&mm->mmap_lock){++++}-{4:4}, at: get_mmap_lock_carefully mm/mmap_lock.c:441 [inline] #1: ffff888053b54378 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x36/0x340 mm/mmap_lock.c:501 stack backtrace: CPU: 0 UID: 0 PID: 22142 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 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+0x1520/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 __fs_reclaim_acquire mm/page_alloc.c:4329 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4343 might_alloc include/linux/sched/mm.h:317 [inline] prepare_alloc_pages+0x15b/0x650 mm/page_alloc.c:5048 __alloc_frozen_pages_noprof+0x12f/0x380 mm/page_alloc.c:5293 alloc_pages_mpol+0x212/0x380 mm/mempolicy.c:2490 folio_alloc_mpol_noprof+0x39/0x160 mm/mempolicy.c:2509 vma_alloc_folio_noprof+0xe1/0x1e0 mm/mempolicy.c:2544 folio_prealloc mm/memory.c:-1 [inline] wp_page_copy mm/memory.c:3875 [inline] do_wp_page+0x1163/0x4c70 mm/memory.c:4336 handle_pte_fault mm/memory.c:6395 [inline] __handle_mm_fault mm/memory.c:6517 [inline] handle_mm_fault+0x1490/0x3080 mm/memory.c:6686 do_user_addr_fault+0x744/0x1340 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:rep_movs_alternative+0x4a/0xa0 arch/x86/lib/copy_user_64.S:74 Code: cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 8b 06 48 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 db 83 f9 08 73 e8 eb c5 a4 e9 bf 61 04 00 48 8b 06 48 89 07 48 8d 47 08 48 83 e0 f8 48 RSP: 0018:ffffc9000d777a58 EFLAGS: 00050206 RAX: ffffffff84d05701 RBX: ffff8880324ca000 RCX: 00000000000002d0 RDX: 0000000000000000 RSI: ffff8880324ca130 RDI: 000056411a20c000 RBP: ffffc9000d777bd8 R08: ffff8880324ca3ff R09: 1ffff1100649947f R10: dffffc0000000000 R11: ffffed1006499480 R12: 1ffff92001aeefaf R13: 000056411a20bed0 R14: ffffc9000d777d88 R15: 0000000000000400 copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline] raw_copy_to_user arch/x86/include/asm/uaccess_64.h:147 [inline] copy_to_user_iter lib/iov_iter.c:25 [inline] iterate_ubuf include/linux/iov_iter.h:30 [inline] iterate_and_advance2 include/linux/iov_iter.h:302 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] _copy_to_iter+0x255/0x1810 lib/iov_iter.c:197 copy_to_iter include/linux/uio.h:220 [inline] seq_read_iter+0xaae/0xca0 fs/seq_file.c:282 new_sync_read fs/read_write.c:493 [inline] vfs_read+0x595/0xa80 fs/read_write.c:574 ksys_read+0x150/0x270 fs/read_write.c:716 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f0ba92a7407 Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007ffd793b8dc0 EFLAGS: 00000202 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007f0ba99a8880 RCX: 00007f0ba92a7407 RDX: 0000000000000400 RSI: 000056411a20bed0 RDI: 0000000000000008 RBP: 00007f0ba93efff0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000a R13: 00007f0ba93efea0 R14: 0000000000000000 R15: 000056411a1e87a0 ---------------- Code disassembly (best guess): 0: cc int3 1: cc int3 2: cc int3 3: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1) a: 00 00 00 d: 0f 1f 00 nopl (%rax) 10: 48 8b 06 mov (%rsi),%rax 13: 48 89 07 mov %rax,(%rdi) 16: 48 83 c6 08 add $0x8,%rsi 1a: 48 83 c7 08 add $0x8,%rdi 1e: 83 e9 08 sub $0x8,%ecx 21: 74 db je 0xfffffffe 23: 83 f9 08 cmp $0x8,%ecx 26: 73 e8 jae 0x10 28: eb c5 jmp 0xffffffef * 2a: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) <-- trapping instruction 2c: e9 bf 61 04 00 jmp 0x461f0 31: 48 8b 06 mov (%rsi),%rax 34: 48 89 07 mov %rax,(%rdi) 37: 48 8d 47 08 lea 0x8(%rdi),%rax 3b: 48 83 e0 f8 and $0xfffffffffffffff8,%rax 3f: 48 rex.W