====================================================== WARNING: possible circular locking dependency detected 6.16.0-syzkaller-08685-g260f6f4fda93 #0 Not tainted ------------------------------------------------------ syz.3.1218/9178 is trying to acquire lock: ffff88801cec8a20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:193 but task is already holding lock: ffff8880446700a8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#24){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x172/0x280 block/blk-mq.c:4400 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4447 loop_add+0x490/0xb70 drivers/block/loop.c:2034 loop_init+0x164/0x270 drivers/block/loop.c:2269 do_one_initcall+0x120/0x6e0 init/main.c:1269 do_initcall_level init/main.c:1331 [inline] do_initcalls init/main.c:1347 [inline] do_basic_setup init/main.c:1366 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1579 kernel_init+0x1c/0x2b0 init/main.c:1469 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4045 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4059 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4130 [inline] slab_alloc_node mm/slub.c:4208 [inline] kmem_cache_alloc_noprof+0x53/0x3b0 mm/slub.c:4235 __kernfs_iattrs+0x124/0x3e0 fs/kernfs/inode.c:36 kernfs_iattrs fs/kernfs/inode.c:61 [inline] __kernfs_setattr+0x4d/0x3c0 fs/kernfs/inode.c:74 kernfs_iop_setattr+0xda/0x120 fs/kernfs/inode.c:128 notify_change+0x6a6/0x1230 fs/attr.c:552 do_truncate+0x1d7/0x230 fs/open.c:68 handle_truncate fs/namei.c:3508 [inline] do_open fs/namei.c:3891 [inline] path_openat+0x2678/0x2cb0 fs/namei.c:4046 do_filp_open+0x20b/0x470 fs/namei.c:4073 do_sys_openat2+0x11b/0x1d0 fs/open.c:1435 do_sys_open fs/open.c:1450 [inline] __do_sys_openat fs/open.c:1466 [inline] __se_sys_openat fs/open.c:1461 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1461 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&root->kernfs_iattr_rwsem){++++}-{4:4}: 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+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 down_read+0x9b/0x480 kernel/locking/rwsem.c:1522 kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x2ac/0x430 fs/stat.c:213 vfs_getattr+0x4a/0x60 fs/stat.c:262 loop_query_min_dio_size.isra.0+0x117/0x250 drivers/block/loop.c:455 loop_assign_backing_file drivers/block/loop.c:508 [inline] loop_change_fd drivers/block/loop.c:586 [inline] lo_ioctl+0x179b/0x20b0 drivers/block/loop.c:1534 lo_compat_ioctl+0xb9/0x170 drivers/block/loop.c:1694 compat_blkdev_ioctl+0x2eb/0x7a0 block/ioctl.c:761 __do_compat_sys_ioctl fs/ioctl.c:696 [inline] __se_compat_sys_ioctl fs/ioctl.c:639 [inline] __ia32_compat_sys_ioctl+0x242/0x370 fs/ioctl.c:639 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0x7c/0x3a0 arch/x86/entry/syscall_32.c:306 do_fast_syscall_32+0x32/0x80 arch/x86/entry/syscall_32.c:331 entry_SYSENTER_compat_after_hwframe+0x84/0x8e other info that might help us debug this: Chain exists of: &root->kernfs_iattr_rwsem --> fs_reclaim --> &q->q_usage_counter(io)#24 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#24); lock(fs_reclaim); lock(&q->q_usage_counter(io)#24); rlock(&root->kernfs_iattr_rwsem); *** DEADLOCK *** 3 locks held by syz.3.1218/9178: #0: ffff8880204e2400 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable+0x30/0xb0 drivers/block/loop.c:118 #1: ffff8880446700a8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 #2: ffff8880446700e0 (&q->q_usage_counter(queue)#20){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 stack backtrace: CPU: 3 UID: 0 PID: 9178 Comm: syz.3.1218 Not tainted 6.16.0-syzkaller-08685-g260f6f4fda93 #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2043 check_noncircular+0x14c/0x170 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+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 down_read+0x9b/0x480 kernel/locking/rwsem.c:1522 kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x2ac/0x430 fs/stat.c:213 vfs_getattr+0x4a/0x60 fs/stat.c:262 loop_query_min_dio_size.isra.0+0x117/0x250 drivers/block/loop.c:455 loop_assign_backing_file drivers/block/loop.c:508 [inline] loop_change_fd drivers/block/loop.c:586 [inline] lo_ioctl+0x179b/0x20b0 drivers/block/loop.c:1534 lo_compat_ioctl+0xb9/0x170 drivers/block/loop.c:1694 compat_blkdev_ioctl+0x2eb/0x7a0 block/ioctl.c:761 __do_compat_sys_ioctl fs/ioctl.c:696 [inline] __se_compat_sys_ioctl fs/ioctl.c:639 [inline] __ia32_compat_sys_ioctl+0x242/0x370 fs/ioctl.c:639 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0x7c/0x3a0 arch/x86/entry/syscall_32.c:306 do_fast_syscall_32+0x32/0x80 arch/x86/entry/syscall_32.c:331 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf7f55579 Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 RSP: 002b:00000000f507655c EFLAGS: 00000296 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000004c06 RDX: 0000000000000006 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 ---------------- Code disassembly (best guess), 2 bytes skipped: 0: 10 06 adc %al,(%rsi) 2: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi 6: 10 07 adc %al,(%rdi) 8: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi c: 10 08 adc %cl,(%rax) e: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi 1e: 00 51 52 add %dl,0x52(%rcx) 21: 55 push %rbp 22: 89 e5 mov %esp,%ebp 24: 0f 34 sysenter 26: cd 80 int $0x80 * 28: 5d pop %rbp <-- trapping instruction 29: 5a pop %rdx 2a: 59 pop %rcx 2b: c3 ret 2c: 90 nop 2d: 90 nop 2e: 90 nop 2f: 90 nop 30: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi 37: 8d b4 26 00 00 00 00 lea 0x0(%rsi,%riz,1),%esi