====================================================== WARNING: possible circular locking dependency detected 6.12.0-syzkaller-05480-gfcc79e1714e8 #0 Not tainted ------------------------------------------------------ syz.8.1501/12335 is trying to acquire lock: ffff888025a52330 (&q->sysfs_lock){+.+.}-{4:4}, at: blk_mq_elv_switch_none block/blk-mq.c:4847 [inline] ffff888025a52330 (&q->sysfs_lock){+.+.}-{4:4}, at: __blk_mq_update_nr_hw_queues block/blk-mq.c:4925 [inline] ffff888025a52330 (&q->sysfs_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x3fa/0x1ae0 block/blk-mq.c:4985 but task is already holding lock: ffff888025a51e00 (&q->q_usage_counter(io)#57){++++}-{0:0}, at: nbd_start_device+0x16c/0xaa0 drivers/block/nbd.c:1413 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&q->q_usage_counter(io)#57){++++}-{0:0}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 __bio_queue_enter+0x60d/0x700 block/blk-core.c:361 bio_queue_enter block/blk.h:79 [inline] blk_mq_submit_bio+0x14b5/0x23a0 block/blk-mq.c:3092 __submit_bio+0x2c6/0x560 block/blk-core.c:629 __submit_bio_noacct_mq block/blk-core.c:710 [inline] submit_bio_noacct_nocheck+0x4d3/0xe30 block/blk-core.c:739 mpage_bio_submit_read fs/mpage.c:75 [inline] mpage_readahead+0x7da/0x930 fs/mpage.c:377 read_pages+0x176/0x830 mm/readahead.c:160 page_cache_ra_unbounded+0x774/0x8a0 mm/readahead.c:290 do_page_cache_ra mm/readahead.c:320 [inline] force_page_cache_ra mm/readahead.c:349 [inline] page_cache_sync_ra+0x3c5/0xad0 mm/readahead.c:562 page_cache_sync_readahead include/linux/pagemap.h:1394 [inline] filemap_get_pages+0x621/0x2540 mm/filemap.c:2547 filemap_read+0x45c/0xf50 mm/filemap.c:2647 blkdev_read_iter+0x2d8/0x430 block/fops.c:767 new_sync_read fs/read_write.c:484 [inline] vfs_read+0x991/0xb70 fs/read_write.c:565 ksys_read+0x18f/0x2b0 fs/read_write.c:708 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (mapping.invalidate_lock#2){++++}-{4:4}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 down_read+0xb1/0xa40 kernel/locking/rwsem.c:1524 filemap_invalidate_lock_shared include/linux/fs.h:873 [inline] filemap_fault+0x6e8/0x1950 mm/filemap.c:3333 __do_fault+0x135/0x460 mm/memory.c:4882 do_shared_fault mm/memory.c:5361 [inline] do_fault mm/memory.c:5435 [inline] do_pte_missing mm/memory.c:3965 [inline] handle_pte_fault+0x1105/0x6820 mm/memory.c:5766 __handle_mm_fault mm/memory.c:5909 [inline] handle_mm_fault+0x1053/0x1ad0 mm/memory.c:6077 do_user_addr_fault arch/x86/mm/fault.c:1389 [inline] handle_page_fault arch/x86/mm/fault.c:1481 [inline] exc_page_fault+0x2b9/0x8c0 arch/x86/mm/fault.c:1539 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 rep_movs_alternative+0x4a/0x70 arch/x86/lib/copy_user_64.S:65 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] _inline_copy_to_user include/linux/uaccess.h:197 [inline] _copy_to_user+0x8b/0xb0 lib/usercopy.c:26 copy_to_user include/linux/uaccess.h:225 [inline] rng_dev_read+0x3e5/0x710 drivers/char/hw_random/core.c:258 do_loop_readv_writev fs/read_write.c:840 [inline] vfs_readv+0x6bc/0xa80 fs/read_write.c:1013 do_preadv fs/read_write.c:1125 [inline] __do_sys_preadv fs/read_write.c:1172 [inline] __se_sys_preadv fs/read_write.c:1167 [inline] __x64_sys_preadv+0x1b7/0x2d0 fs/read_write.c:1167 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (&mm->mmap_lock){++++}-{4:4}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 __might_fault+0xc6/0x120 mm/memory.c:6716 _inline_copy_from_user include/linux/uaccess.h:162 [inline] _copy_from_user+0x2a/0xc0 lib/usercopy.c:18 copy_from_user include/linux/uaccess.h:212 [inline] __blk_trace_setup kernel/trace/blktrace.c:626 [inline] blk_trace_ioctl+0x1ad/0x9a0 kernel/trace/blktrace.c:740 blkdev_ioctl+0x40c/0x6a0 block/ioctl.c:682 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&q->debugfs_mutex){+.+.}-{4:4}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735 blk_register_queue+0x156/0x460 block/blk-sysfs.c:774 add_disk_fwnode+0x648/0xf80 block/genhd.c:493 add_disk include/linux/blkdev.h:751 [inline] brd_alloc+0x547/0x790 drivers/block/brd.c:399 brd_init+0x126/0x1b0 drivers/block/brd.c:479 do_one_initcall+0x248/0x880 init/main.c:1266 do_initcall_level+0x157/0x210 init/main.c:1328 do_initcalls+0x3f/0x80 init/main.c:1344 kernel_init_freeable+0x435/0x5d0 init/main.c:1577 kernel_init+0x1d/0x2b0 init/main.c:1466 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 -> #0 (&q->sysfs_lock){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/locking/lockdep.c:3280 [inline] validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735 blk_mq_elv_switch_none block/blk-mq.c:4847 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:4925 [inline] blk_mq_update_nr_hw_queues+0x3fa/0x1ae0 block/blk-mq.c:4985 nbd_start_device+0x16c/0xaa0 drivers/block/nbd.c:1413 nbd_start_device_ioctl drivers/block/nbd.c:1464 [inline] __nbd_ioctl drivers/block/nbd.c:1539 [inline] nbd_ioctl+0x5dc/0xf40 drivers/block/nbd.c:1579 blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &q->sysfs_lock --> mapping.invalidate_lock#2 --> &q->q_usage_counter(io)#57 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#57); lock(mapping.invalidate_lock#2); lock(&q->q_usage_counter(io)#57); lock(&q->sysfs_lock); *** DEADLOCK *** 4 locks held by syz.8.1501/12335: #0: ffff8880260a2198 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_ioctl+0x13c/0xf40 drivers/block/nbd.c:1572 #1: ffff8880260a20d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0xc2/0x1ae0 block/blk-mq.c:4984 #2: ffff888025a51e00 (&q->q_usage_counter(io)#57){++++}-{0:0}, at: nbd_start_device+0x16c/0xaa0 drivers/block/nbd.c:1413 #3: ffff888025a51e38 (&q->q_usage_counter(queue)#41){+.+.}-{0:0}, at: nbd_start_device+0x16c/0xaa0 drivers/block/nbd.c:1413 stack backtrace: CPU: 1 UID: 0 PID: 12335 Comm: syz.8.1501 Not tainted 6.12.0-syzkaller-05480-gfcc79e1714e8 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206 check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/locking/lockdep.c:3280 [inline] validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735 blk_mq_elv_switch_none block/blk-mq.c:4847 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:4925 [inline] blk_mq_update_nr_hw_queues+0x3fa/0x1ae0 block/blk-mq.c:4985 nbd_start_device+0x16c/0xaa0 drivers/block/nbd.c:1413 nbd_start_device_ioctl drivers/block/nbd.c:1464 [inline] __nbd_ioctl drivers/block/nbd.c:1539 [inline] nbd_ioctl+0x5dc/0xf40 drivers/block/nbd.c:1579 blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f1205b7e819 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f120693f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f1205d36080 RCX: 00007f1205b7e819 RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000004 RBP: 00007f1205bf175e R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f1205d36080 R15: 00007ffd13786858