====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ syz.6.6419/24803 is trying to acquire lock: ffff888025aabbc0 (&q->blkcg_mutex){+.+.}-{4:4}, at: blkcg_deactivate_policy+0x167/0x600 block/blk-cgroup.c:1681 but task is already holding lock: ffff8880254238b8 (&eq->sysfs_lock){+.+.}-{4:4}, at: elevator_exit+0x88/0xf0 block/elevator.c:160 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&eq->sysfs_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 elevator_exit+0x88/0xf0 block/elevator.c:160 elevator_switch+0x3a7/0x7e0 block/elevator.c:580 elevator_change+0x352/0x530 block/elevator.c:681 elevator_set_none+0x92/0xf0 block/elevator.c:769 blk_unregister_queue+0x178/0x310 block/blk-sysfs.c:1073 __del_gendisk+0x2e3/0xb20 block/genhd.c:739 del_gendisk+0x10e/0x1b0 block/genhd.c:819 loop_remove drivers/block/loop.c:2112 [inline] loop_control_remove drivers/block/loop.c:2171 [inline] loop_control_ioctl+0x4f8/0x620 drivers/block/loop.c:2213 __do_compat_sys_ioctl fs/ioctl.c:695 [inline] __se_compat_sys_ioctl fs/ioctl.c:638 [inline] __ia32_compat_sys_ioctl+0x2cf/0x360 fs/ioctl.c:638 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e -> #4 (&q->elevator_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 elevator_change+0x1bc/0x530 block/elevator.c:679 elv_iosched_store+0x3be/0x460 block/elevator.c:826 queue_attr_store+0x25f/0x2f0 block/blk-sysfs.c:906 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6ac/0x1050 fs/read_write.c:687 ksys_write+0x12a/0x250 fs/read_write.c:739 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e -> #3 (&q->q_usage_counter(io)#17){++++}-{0:0}: lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 blk_alloc_queue+0x610/0x790 block/blk-core.c:504 blk_mq_alloc_queue+0x174/0x290 block/blk-mq.c:4420 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4467 loop_add+0x498/0xb60 drivers/block/loop.c:2041 loop_init+0x1d3/0x200 drivers/block/loop.c:2280 do_one_initcall+0x11d/0x700 init/main.c:1347 do_initcall_level init/main.c:1409 [inline] do_initcalls init/main.c:1425 [inline] do_basic_setup init/main.c:1445 [inline] kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658 kernel_init+0x1f/0x1e0 init/main.c:1548 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (fs_reclaim){+.+.}-{0:0}: lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __fs_reclaim_acquire mm/page_alloc.c:4329 [inline] fs_reclaim_acquire+0xc4/0x100 mm/page_alloc.c:4343 might_alloc include/linux/sched/mm.h:317 [inline] prepare_alloc_pages+0x166/0x5f0 mm/page_alloc.c:5048 __alloc_frozen_pages_noprof+0x1af/0x2dc0 mm/page_alloc.c:5293 __alloc_pages_noprof+0xb/0x110 mm/page_alloc.c:5338 __alloc_pages_node_noprof include/linux/gfp.h:291 [inline] alloc_pages_node_noprof include/linux/gfp.h:318 [inline] pcpu_alloc_pages mm/percpu-vm.c:95 [inline] pcpu_populate_chunk+0x118/0x990 mm/percpu-vm.c:285 pcpu_alloc_noprof+0x881/0x1ca0 mm/percpu.c:1876 iommu_dma_init_fq_percpu drivers/iommu/dma-iommu.c:321 [inline] iommu_dma_init_fq+0x1da/0x7e0 drivers/iommu/dma-iommu.c:347 iommu_dma_init_domain drivers/iommu/dma-iommu.c:720 [inline] iommu_setup_dma_ops+0x11df/0x1620 drivers/iommu/dma-iommu.c:2159 bus_iommu_probe+0x264/0x550 drivers/iommu/iommu.c:1983 iommu_device_register+0x1af/0x280 drivers/iommu/iommu.c:307 intel_iommu_init+0x2020/0x2990 drivers/iommu/intel/iommu.c:2662 pci_iommu_init+0x3c/0x80 arch/x86/kernel/pci-dma.c:174 do_one_initcall+0x11d/0x700 init/main.c:1347 do_initcall_level init/main.c:1409 [inline] do_initcalls init/main.c:1425 [inline] do_basic_setup init/main.c:1445 [inline] kernel_init_freeable+0x6ea/0x7b0 init/main.c:1658 kernel_init+0x1f/0x1e0 init/main.c:1548 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (pcpu_alloc_mutex){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 pcpu_alloc_noprof+0xe87/0x1ca0 mm/percpu.c:1788 percpu_ref_init+0x37/0x3f0 lib/percpu-refcount.c:72 blkg_alloc+0xf0/0xf80 block/blk-cgroup.c:313 blkg_conf_prep+0x46e/0xf10 block/blk-cgroup.c:873 tg_set_conf.isra.0+0x1ed/0x500 block/blk-throttle.c:1373 cgroup_file_write+0x1e6/0x8a0 kernel/cgroup/cgroup.c:4316 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6ac/0x1050 fs/read_write.c:687 ksys_write+0x12a/0x250 fs/read_write.c:739 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e -> #0 (&q->blkcg_mutex){+.+.}-{4:4}: check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165 check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 blkcg_deactivate_policy+0x167/0x600 block/blk-cgroup.c:1681 bfq_exit_queue+0x29d/0x430 block/bfq-iosched.c:7165 blk_mq_exit_sched+0x20e/0x4e0 block/blk-mq-sched.c:702 elevator_exit+0x93/0xf0 block/elevator.c:161 elevator_switch+0x3a7/0x7e0 block/elevator.c:580 elevator_change+0x352/0x530 block/elevator.c:681 elevator_set_none+0x92/0xf0 block/elevator.c:769 blk_unregister_queue+0x178/0x310 block/blk-sysfs.c:1073 __del_gendisk+0x2e3/0xb20 block/genhd.c:739 del_gendisk+0x10e/0x1b0 block/genhd.c:819 loop_remove drivers/block/loop.c:2112 [inline] loop_control_remove drivers/block/loop.c:2171 [inline] loop_control_ioctl+0x4f8/0x620 drivers/block/loop.c:2213 __do_compat_sys_ioctl fs/ioctl.c:695 [inline] __se_compat_sys_ioctl fs/ioctl.c:638 [inline] __ia32_compat_sys_ioctl+0x2cf/0x360 fs/ioctl.c:638 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e other info that might help us debug this: Chain exists of: &q->blkcg_mutex --> &q->elevator_lock --> &eq->sysfs_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&eq->sysfs_lock); lock(&q->elevator_lock); lock(&eq->sysfs_lock); lock(&q->blkcg_mutex); *** DEADLOCK *** 3 locks held by syz.6.6419/24803: #0: ffff888025af53a0 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0x106/0x1b0 block/genhd.c:818 #1: ffff888025aabd68 (&q->elevator_lock){+.+.}-{4:4}, at: elevator_change+0x1bc/0x530 block/elevator.c:679 #2: ffff8880254238b8 (&eq->sysfs_lock){+.+.}-{4:4}, at: elevator_exit+0x88/0xf0 block/elevator.c:160 stack backtrace: CPU: 3 UID: 60928 PID: 24803 Comm: syz.6.6419 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165 check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821 blkcg_deactivate_policy+0x167/0x600 block/blk-cgroup.c:1681 bfq_exit_queue+0x29d/0x430 block/bfq-iosched.c:7165 blk_mq_exit_sched+0x20e/0x4e0 block/blk-mq-sched.c:702 elevator_exit+0x93/0xf0 block/elevator.c:161 elevator_switch+0x3a7/0x7e0 block/elevator.c:580 elevator_change+0x352/0x530 block/elevator.c:681 elevator_set_none+0x92/0xf0 block/elevator.c:769 blk_unregister_queue+0x178/0x310 block/blk-sysfs.c:1073 __del_gendisk+0x2e3/0xb20 block/genhd.c:739 del_gendisk+0x10e/0x1b0 block/genhd.c:819 loop_remove drivers/block/loop.c:2112 [inline] loop_control_remove drivers/block/loop.c:2171 [inline] loop_control_ioctl+0x4f8/0x620 drivers/block/loop.c:2213 __do_compat_sys_ioctl fs/ioctl.c:695 [inline] __se_compat_sys_ioctl fs/ioctl.c:638 [inline] __ia32_compat_sys_ioctl+0x2cf/0x360 fs/ioctl.c:638 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf709efec Code: Unable to access opcode bytes at 0xf709efc2. RSP: 002b:00000000f548d50c EFLAGS: 00000292 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 0000000000004c81 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000