======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.12007/1344 is trying to acquire lock:
ffffffff8ea852e0 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages+0x15b/0x650

but task is already holding lock:
ffff888111db1bb8 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x36/0x340

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
       _copy_from_user+0x28/0xb0
       csum_and_copy_from_iter_full+0x210/0x1fb0
       ip_generic_getfrag+0x149/0x2d0
       __ip6_append_data+0x3aef/0x4080
       ip6_append_data+0x108/0x270
       rawv6_sendmsg+0x1298/0x18c0
       ____sys_sendmsg+0x853/0xa20
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1bd/0x2a0
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100
       inet_shutdown+0x6a/0x390
       nbd_mark_nsock_dead+0x2cb/0x550
       recv_work+0x1cef/0x1e10
       process_scheduled_works+0xa8e/0x14e0
       worker_thread+0xa47/0xfb0
       kthread+0x388/0x470
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1590
       nbd_queue_rq+0x373/0x1150
       blk_mq_dispatch_rq_list+0x499/0x1990
       __blk_mq_sched_dispatch_requests+0xd36/0x1580
       blk_mq_sched_dispatch_requests+0xd7/0x190
       blk_mq_run_hw_queue+0x348/0x4f0
       blk_mq_dispatch_list+0xd11/0xe10
       blk_mq_flush_plug_list+0x45f/0x540
       __blk_flush_plug+0x3ed/0x4d0
       __submit_bio+0x465/0x560
       submit_bio_noacct_nocheck+0x2f4/0xa40
       block_read_full_folio+0x581/0x810
       filemap_read_folio+0x12c/0x3a0
       do_read_cache_folio+0x354/0x590
       read_part_sector+0xb6/0x2b0
       adfspart_check_ICS+0xb1/0x960
       bdev_disk_changed+0x82b/0x1780
       blkdev_get_whole+0x372/0x510
       bdev_open+0x324/0xd70
       blkdev_open+0x461/0x600
       do_dentry_open+0x816/0x1380
       vfs_open+0x3b/0x340
       path_openat+0x2e44/0x3830
       do_file_open+0x23e/0x4a0
       do_sys_openat2+0x115/0x200
       __x64_sys_openat+0x138/0x170
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1590
       nbd_queue_rq+0xc1/0x1150
       blk_mq_dispatch_rq_list+0x499/0x1990
       __blk_mq_sched_dispatch_requests+0xd36/0x1580
       blk_mq_sched_dispatch_requests+0xd7/0x190
       blk_mq_run_hw_queue+0x348/0x4f0
       blk_mq_dispatch_list+0xd11/0xe10
       blk_mq_flush_plug_list+0x45f/0x540
       __blk_flush_plug+0x3ed/0x4d0
       __submit_bio+0x465/0x560
       submit_bio_noacct_nocheck+0x2f4/0xa40
       block_read_full_folio+0x581/0x810
       filemap_read_folio+0x12c/0x3a0
       do_read_cache_folio+0x354/0x590
       read_part_sector+0xb6/0x2b0
       adfspart_check_ICS+0xb1/0x960
       bdev_disk_changed+0x82b/0x1780
       blkdev_get_whole+0x372/0x510
       bdev_open+0x324/0xd70
       blkdev_open+0x461/0x600
       do_dentry_open+0x816/0x1380
       vfs_open+0x3b/0x340
       path_openat+0x2e44/0x3830
       do_file_open+0x23e/0x4a0
       do_sys_openat2+0x115/0x200
       __x64_sys_openat+0x138/0x170
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (set->srcu){.+.+}-{0:0}:
       __synchronize_srcu+0xc9/0x2f0
       elevator_switch+0x1e8/0x7b0
       elevator_change+0x2fa/0x480
       elevator_set_default+0x375/0x440
       blk_register_queue+0x3f3/0x4e0
       __add_disk+0x6cb/0xe30
       add_disk_fwnode+0xfb/0x4b0
       nbd_dev_add+0x733/0xb60
       nbd_init+0x15f/0x1e0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x1d/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #2 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1590
       elevator_change+0x1af/0x480
       elevator_set_none+0xb5/0x140
       blk_mq_update_nr_hw_queues+0x5ef/0x19f0
       nbd_start_device+0x189/0xb30
       nbd_genl_connect+0x1597/0x1c10
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x7bb/0x940
       netlink_sendmsg+0x813/0xb40
       ____sys_sendmsg+0x9b9/0xa20
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1bd/0x2a0
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#49){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690
       __blk_mq_alloc_disk+0x194/0x390
       nbd_dev_add+0x494/0xb60
       nbd_init+0x15f/0x1e0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x1d/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #0 (fs_reclaim){+.+.}-{0:0}:
       __lock_acquire+0x1520/0x2cd0
       lock_acquire+0x106/0x350
       fs_reclaim_acquire+0x71/0x100
       prepare_alloc_pages+0x15b/0x650
       __alloc_frozen_pages_noprof+0x12f/0x380
       alloc_pages_mpol+0x212/0x380
       folio_alloc_mpol_noprof+0x39/0x160
       shmem_alloc_and_add_folio+0x43e/0xf60
       shmem_get_folio_gfp+0x5b2/0x16c0
       shmem_fault+0x179/0x390
       __do_fault+0x138/0x2a0
       do_pte_missing+0x6e1/0x3540
       handle_mm_fault+0x1b36/0x3080
       do_user_addr_fault+0x744/0x1340
       exc_page_fault+0x6a/0xc0
       asm_exc_page_fault+0x26/0x30
       rep_movs_alternative+0x33/0x90
       _copy_to_user+0x8a/0xb0
       br_ioctl_stub+0xcb3/0xd60
       sock_ioctl+0x4e1/0x7e0
       __se_sys_ioctl+0xfc/0x170
       do_syscall_64+0x174/0x580
       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 ***

3 locks held by syz.1.12007/1344:
 #0: ffffffff8fda5760 (br_ioctl_mutex){+.+.}-{4:4}, at: sock_ioctl+0x4b8/0x7e0
 #1: ffffffff8fdc4b00 (rtnl_mutex){+.+.}-{4:4}, at: br_ioctl_stub+0x1a8/0xd60
 #2: ffff888111db1bb8 (&mm->mmap_lock){++++}-{4:4}, at: lock_mm_and_find_vma+0x36/0x340

stack backtrace:
CPU: 0 UID: 0 PID: 1344 Comm: syz.1.12007 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_circular_bug+0x2e1/0x300
 check_noncircular+0x12e/0x150
 __lock_acquire+0x1520/0x2cd0
 lock_acquire+0x106/0x350
 fs_reclaim_acquire+0x71/0x100
 prepare_alloc_pages+0x15b/0x650
 __alloc_frozen_pages_noprof+0x12f/0x380
 alloc_pages_mpol+0x212/0x380
 folio_alloc_mpol_noprof+0x39/0x160
 shmem_alloc_and_add_folio+0x43e/0xf60
 shmem_get_folio_gfp+0x5b2/0x16c0
 shmem_fault+0x179/0x390
 __do_fault+0x138/0x2a0
 do_pte_missing+0x6e1/0x3540
 handle_mm_fault+0x1b36/0x3080
 do_user_addr_fault+0x744/0x1340
 exc_page_fault+0x6a/0xc0
 asm_exc_page_fault+0x26/0x30
RIP: 0010:rep_movs_alternative+0x33/0x90
Code: 73 25 85 c9 74 0f 8a 06 88 07 48 ff c7 48 ff c6 48 ff c9 75 f1 c3 cc 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
RSP: 0018:ffffc9000345fba8 EFLAGS: 00010216
RAX: 0000004f0000000d RBX: 0000000000000020 RCX: 0000000000000020
RDX: 0000000000000000 RSI: ffff888024147780 RDI: 00002000000010c0
RBP: ffffc9000345fdb0 R08: ffff88802414779f R09: 1ffff11004828ef3
R10: dffffc0000000000 R11: ffffed1004828ef4 R12: 00002000000010e0
R13: 00007ffffffff000 R14: ffff888024147780 R15: 00002000000010c0
 _copy_to_user+0x8a/0xb0
 br_ioctl_stub+0xcb3/0xd60
 sock_ioctl+0x4e1/0x7e0
 __se_sys_ioctl+0xfc/0x170
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1e3299ce59
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:00007f1e338b3028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1e32c15fa0 RCX: 00007f1e3299ce59
RDX: 0000200000000040 RSI: 0000000000008941 RDI: 0000000000000003
RBP: 00007f1e32a32e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1e32c16038 R14: 00007f1e32c15fa0 R15: 00007ffebaa3a618
 </TASK>
