====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ udevd/6044 is trying to acquire lock: ffffffff8e448540 ( fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline] fs_reclaim){+.+.}-{0:0}, at: mempool_alloc_noprof+0xa7/0x380 mm/mempool.c:559 but task is already holding lock: ffff888141b6c518 (set->srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:185 [inline] ffff888141b6c518 (set->srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:277 [inline] ffff888141b6c518 (set->srcu){.+.+}-{0:0}, at: blk_mq_dispatch_queue_requests+0x5f9/0x800 block/blk-mq.c:2897 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (set->srcu){.+.+}-{0:0}: lock_sync+0xba/0x160 kernel/locking/lockdep.c:5916 srcu_lock_sync include/linux/srcu.h:197 [inline] __synchronize_srcu+0x96/0x3a0 kernel/rcu/srcutree.c:1503 blk_throtl_init+0x298/0x410 block/blk-throttle.c:1324 tg_set_conf+0x1c6/0x4b0 block/blk-throttle.c:1359 cgroup_file_write+0x3a1/0x740 kernel/cgroup/cgroup.c:4312 kernfs_fop_write_iter+0x3af/0x540 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x5c9/0xb30 fs/read_write.c:686 ksys_write+0x145/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&q->q_usage_counter(io)#17){++++}-{0:0}: lock_acquire+0x117/0x350 kernel/locking/lockdep.c:5868 blk_alloc_queue+0x538/0x620 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4410 [inline] __blk_mq_alloc_disk+0x15c/0x340 block/blk-mq.c:4457 loop_add+0x411/0xad0 drivers/block/loop.c:2206 loop_init+0xd9/0x170 drivers/block/loop.c:2441 do_one_initcall+0x1fb/0x870 init/main.c:1378 do_initcall_level+0x104/0x190 init/main.c:1440 do_initcalls+0x59/0xa0 init/main.c:1456 kernel_init_freeable+0x334/0x4b0 init/main.c:1688 kernel_init+0x1d/0x1d0 init/main.c:1578 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 -> #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+0xb9b/0x2130 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x117/0x350 kernel/locking/lockdep.c:5868 __fs_reclaim_acquire mm/page_alloc.c:4301 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4315 might_alloc include/linux/sched/mm.h:317 [inline] mempool_alloc_noprof+0xa7/0x380 mm/mempool.c:559 bio_alloc_bioset+0x241/0x12a0 block/bio.c:559 __blkdev_direct_IO_async block/fops.c:338 [inline] blkdev_direct_IO+0x9c0/0x17e0 block/fops.c:437 blkdev_read_iter+0x23d/0x440 block/fops.c:845 lo_submit_rw_aio+0x488/0x620 drivers/block/loop.c:-1 lo_rw_aio_nowait drivers/block/loop.c:513 [inline] loop_queue_rq+0x6c5/0x8d0 drivers/block/loop.c:2036 __blk_mq_issue_directly block/blk-mq.c:2714 [inline] blk_mq_request_issue_directly+0x3c1/0x710 block/blk-mq.c:2801 blk_mq_issue_direct+0x2a0/0x660 block/blk-mq.c:2822 blk_mq_dispatch_queue_requests+0x621/0x800 block/blk-mq.c:2897 blk_mq_flush_plug_list+0x432/0x550 block/blk-mq.c:2980 __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225 blk_finish_plug block/blk-core.c:1252 [inline] __submit_bio+0x2d3/0x5a0 block/blk-core.c:651 __submit_bio_noacct_mq block/blk-core.c:724 [inline] submit_bio_noacct_nocheck+0x2eb/0xa50 block/blk-core.c:755 submit_bh fs/buffer.c:2829 [inline] block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461 filemap_read_folio+0x117/0x380 mm/filemap.c:2496 filemap_update_page mm/filemap.c:2583 [inline] filemap_get_pages+0x1692/0x1df0 mm/filemap.c:2713 filemap_read+0x3f6/0x11a0 mm/filemap.c:2800 blkdev_read_iter+0x30a/0x440 block/fops.c:861 new_sync_read fs/read_write.c:491 [inline] vfs_read+0x55a/0xa30 fs/read_write.c:572 ksys_read+0x145/0x250 fs/read_write.c:715 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 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 --> &q->q_usage_counter(io)#17 --> set->srcu Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(set->srcu); lock(&q->q_usage_counter(io)#17); lock(set->srcu); lock(fs_reclaim); *** DEADLOCK *** 3 locks held by udevd/6044: #0: ffff8880234c7aa8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1042 [inline] #0: ffff8880234c7aa8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: blkdev_read_iter+0x2f8/0x440 block/fops.c:860 #1: ffff8880234c7c48 (mapping.invalidate_lock){++++}-{4:4}, at: filemap_invalidate_lock_shared include/linux/fs.h:1092 [inline] #1: ffff8880234c7c48 (mapping.invalidate_lock){++++}-{4:4}, at: filemap_update_page mm/filemap.c:2549 [inline] #1: ffff8880234c7c48 (mapping.invalidate_lock){++++}-{4:4}, at: filemap_get_pages+0x8d9/0x1df0 mm/filemap.c:2713 #2: ffff888141b6c518 (set->srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:185 [inline] #2: ffff888141b6c518 (set->srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:277 [inline] #2: ffff888141b6c518 (set->srcu){.+.+}-{0:0}, at: blk_mq_dispatch_queue_requests+0x5f9/0x800 block/blk-mq.c:2897 stack backtrace: CPU: 1 UID: 0 PID: 6044 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 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+0xb9b/0x2130 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x117/0x350 kernel/locking/lockdep.c:5868 __fs_reclaim_acquire mm/page_alloc.c:4301 [inline] fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4315 might_alloc include/linux/sched/mm.h:317 [inline] mempool_alloc_noprof+0xa7/0x380 mm/mempool.c:559 bio_alloc_bioset+0x241/0x12a0 block/bio.c:559 __blkdev_direct_IO_async block/fops.c:338 [inline] blkdev_direct_IO+0x9c0/0x17e0 block/fops.c:437 blkdev_read_iter+0x23d/0x440 block/fops.c:845 lo_submit_rw_aio+0x488/0x620 drivers/block/loop.c:-1 lo_rw_aio_nowait drivers/block/loop.c:513 [inline] loop_queue_rq+0x6c5/0x8d0 drivers/block/loop.c:2036 __blk_mq_issue_directly block/blk-mq.c:2714 [inline] blk_mq_request_issue_directly+0x3c1/0x710 block/blk-mq.c:2801 blk_mq_issue_direct+0x2a0/0x660 block/blk-mq.c:2822 blk_mq_dispatch_queue_requests+0x621/0x800 block/blk-mq.c:2897 blk_mq_flush_plug_list+0x432/0x550 block/blk-mq.c:2980 __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225 blk_finish_plug block/blk-core.c:1252 [inline] __submit_bio+0x2d3/0x5a0 block/blk-core.c:651 __submit_bio_noacct_mq block/blk-core.c:724 [inline] submit_bio_noacct_nocheck+0x2eb/0xa50 block/blk-core.c:755 submit_bh fs/buffer.c:2829 [inline] block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461 filemap_read_folio+0x117/0x380 mm/filemap.c:2496 filemap_update_page mm/filemap.c:2583 [inline] filemap_get_pages+0x1692/0x1df0 mm/filemap.c:2713 filemap_read+0x3f6/0x11a0 mm/filemap.c:2800 blkdev_read_iter+0x30a/0x440 block/fops.c:861 new_sync_read fs/read_write.c:491 [inline] vfs_read+0x55a/0xa30 fs/read_write.c:572 ksys_read+0x145/0x250 fs/read_write.c:715 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f9b05ca7407 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:00007ffc5e2cefa0 EFLAGS: 00000202 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007f9b06389880 RCX: 00007f9b05ca7407 RDX: 0000000000000200 RSI: 00007f9b06388000 RDI: 0000000000000009 RBP: 0000555786c71050 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 R13: 0000000000000000 R14: 0000555786c7d508 R15: 00007f9b064b039c