====================================================== WARNING: possible circular locking dependency detected 6.13.0-rc3-syzkaller-00044-gaef25be35d23 #0 Not tainted ------------------------------------------------------ syz.4.1908/12938 is trying to acquire lock: ffff888056d4d430 (&sb->s_type->i_mutex_key#21){++++}-{4:4}, at: inode_lock include/linux/fs.h:818 [inline] ffff888056d4d430 (&sb->s_type->i_mutex_key#21){++++}-{4:4}, at: __generic_file_fsync+0x97/0x1a0 fs/libfs.c:1536 but task is already holding lock: ffff8880253ff608 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: loop_set_status+0x1e4/0x8f0 drivers/block/loop.c:1267 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#26){++++}-{0:0}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 bio_queue_enter block/blk.h:75 [inline] blk_mq_submit_bio+0x1536/0x2390 block/blk-mq.c:3090 __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 submit_bh fs/buffer.c:2819 [inline] __bh_read fs/buffer.c:3088 [inline] bh_readahead include/linux/buffer_head.h:433 [inline] __breadahead+0x1a4/0x240 fs/buffer.c:1444 sb_breadahead include/linux/buffer_head.h:358 [inline] fat_dir_readahead fs/fat/dir.c:67 [inline] fat__get_entry fs/fat/dir.c:98 [inline] fat_get_entry+0x697/0xae0 fs/fat/dir.c:128 fat_get_short_entry fs/fat/dir.c:885 [inline] fat_subdirs+0x132/0x3c0 fs/fat/dir.c:951 fat_fill_inode+0xf80/0x16c0 fs/fat/inode.c:535 fat_build_inode+0x28e/0x3d0 fs/fat/inode.c:608 vfat_lookup+0x2f0/0x4f0 fs/fat/namei_vfat.c:721 lookup_open fs/namei.c:3627 [inline] open_last_lookups fs/namei.c:3748 [inline] path_openat+0x11a9/0x3590 fs/namei.c:3984 do_filp_open+0x27f/0x4e0 fs/namei.c:4014 do_sys_openat2+0x13e/0x1d0 fs/open.c:1402 do_sys_open fs/open.c:1417 [inline] __do_sys_openat fs/open.c:1433 [inline] __se_sys_openat fs/open.c:1428 [inline] __x64_sys_openat+0x247/0x2a0 fs/open.c:1428 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 (&sbi->s_lock){+.+.}-{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 vfat_lookup+0xee/0x4f0 fs/fat/namei_vfat.c:710 lookup_open fs/namei.c:3627 [inline] open_last_lookups fs/namei.c:3748 [inline] path_openat+0x11a9/0x3590 fs/namei.c:3984 do_filp_open+0x27f/0x4e0 fs/namei.c:4014 do_sys_openat2+0x13e/0x1d0 fs/open.c:1402 do_sys_open fs/open.c:1417 [inline] __do_sys_openat fs/open.c:1433 [inline] __se_sys_openat fs/open.c:1428 [inline] __x64_sys_openat+0x247/0x2a0 fs/open.c:1428 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 -> #0 (&sb->s_type->i_mutex_key#21){++++}-{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 down_write+0x99/0x220 kernel/locking/rwsem.c:1577 inode_lock include/linux/fs.h:818 [inline] __generic_file_fsync+0x97/0x1a0 fs/libfs.c:1536 fat_file_fsync+0x7b/0x190 fs/fat/file.c:191 __loop_update_dio+0x1a4/0x500 drivers/block/loop.c:204 loop_set_status+0x62b/0x8f0 drivers/block/loop.c:1289 lo_ioctl+0xcbc/0x1f50 blkdev_ioctl+0x57f/0x6a0 block/ioctl.c:693 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf7/0x170 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: &sb->s_type->i_mutex_key#21 --> &sbi->s_lock --> &q->q_usage_counter(io)#26 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#26); lock(&sbi->s_lock); lock(&q->q_usage_counter(io)#26); lock(&sb->s_type->i_mutex_key#21); *** DEADLOCK *** 3 locks held by syz.4.1908/12938: #0: ffff88802542eb60 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x2a/0x8f0 drivers/block/loop.c:1251 #1: ffff8880253ff608 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: loop_set_status+0x1e4/0x8f0 drivers/block/loop.c:1267 #2: ffff8880253ff640 (&q->q_usage_counter(queue)#10){+.+.}-{0:0}, at: loop_set_status+0x1e4/0x8f0 drivers/block/loop.c:1267 stack backtrace: CPU: 0 UID: 0 PID: 12938 Comm: syz.4.1908 Not tainted 6.13.0-rc3-syzkaller-00044-gaef25be35d23 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024 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 down_write+0x99/0x220 kernel/locking/rwsem.c:1577 inode_lock include/linux/fs.h:818 [inline] __generic_file_fsync+0x97/0x1a0 fs/libfs.c:1536 fat_file_fsync+0x7b/0x190 fs/fat/file.c:191 __loop_update_dio+0x1a4/0x500 drivers/block/loop.c:204 loop_set_status+0x62b/0x8f0 drivers/block/loop.c:1289 lo_ioctl+0xcbc/0x1f50 blkdev_ioctl+0x57f/0x6a0 block/ioctl.c:693 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf7/0x170 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: 0033:0x7f2638d85d29 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:00007f2639acf038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f2638f75fa0 RCX: 00007f2638d85d29 RDX: 0000000020000480 RSI: 0000000000004c02 RDI: 0000000000000004 RBP: 00007f2638e01a20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f2638f75fa0 R15: 00007ffea90a3f18