====================================================== WARNING: possible circular locking dependency detected 6.12.0-syzkaller-11930-g0e287d31b62b #0 Not tainted ------------------------------------------------------ syz.3.565/7542 is trying to acquire lock: ffff88805a15c7a0 (&sb->s_type->i_mutex_key#24){++++}-{4:4}, at: inode_lock include/linux/fs.h:818 [inline] ffff88805a15c7a0 (&sb->s_type->i_mutex_key#24){++++}-{4:4}, at: __generic_file_fsync+0xb0/0x1f0 fs/libfs.c:1536 but task is already holding lock: ffff8880259e9e00 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: loop_set_status+0x1d9/0x700 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)#17){++++}-{0:0}: bio_queue_enter block/blk.h:75 [inline] blk_mq_submit_bio+0x1fb6/0x24c0 block/blk-mq.c:3092 __submit_bio+0x384/0x540 block/blk-core.c:629 __submit_bio_noacct_mq block/blk-core.c:710 [inline] submit_bio_noacct_nocheck+0x698/0xd70 block/blk-core.c:739 submit_bio_noacct+0x93a/0x1e20 block/blk-core.c:868 submit_bh fs/buffer.c:2819 [inline] __bread_slow fs/buffer.c:1264 [inline] __bread_gfp+0x189/0x340 fs/buffer.c:1488 sb_bread include/linux/buffer_head.h:346 [inline] fat_ent_bread+0x16b/0x330 fs/fat/fatent.c:109 fat_ent_read_block fs/fat/fatent.c:445 [inline] fat_alloc_clusters+0x58b/0xf80 fs/fat/fatent.c:493 fat_add_new_entries+0x230/0xf50 fs/fat/dir.c:1230 fat_add_entries+0xc34/0x1530 fs/fat/dir.c:1388 vfat_add_entry+0x298d/0x2fe0 fs/fat/namei_vfat.c:677 vfat_create+0x15f/0x2c0 fs/fat/namei_vfat.c:771 lookup_open.isra.0+0x1177/0x14c0 fs/namei.c:3649 open_last_lookups fs/namei.c:3748 [inline] path_openat+0x904/0x2d60 fs/namei.c:3984 do_filp_open+0x20c/0x470 fs/namei.c:4014 do_sys_openat2+0x17a/0x1e0 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+0x175/0x210 fs/open.c:1428 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&sbi->fat_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x19b/0xa60 kernel/locking/mutex.c:735 lock_fat fs/fat/fatent.c:281 [inline] fat_alloc_clusters+0x1b9/0xf80 fs/fat/fatent.c:477 fat_add_cluster+0x79/0x100 fs/fat/inode.c:107 __fat_get_block fs/fat/inode.c:154 [inline] fat_get_block+0x38e/0xaf0 fs/fat/inode.c:189 __block_write_begin_int+0x4fe/0x16e0 fs/buffer.c:2116 block_write_begin+0x9a/0x1d0 fs/buffer.c:2226 cont_write_begin+0x61d/0x950 fs/buffer.c:2577 fat_write_begin+0x66/0x150 fs/fat/inode.c:228 generic_perform_write+0x2bd/0x920 mm/filemap.c:4055 __generic_file_write_iter+0x1f7/0x240 mm/filemap.c:4156 generic_file_write_iter+0xe1/0x340 mm/filemap.c:4182 new_sync_write fs/read_write.c:586 [inline] vfs_write+0x5b1/0x1150 fs/read_write.c:679 ksys_write+0x12b/0x250 fs/read_write.c:731 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&sb->s_type->i_mutex_key#24){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/locking/lockdep.c:3280 [inline] validate_chain kernel/locking/lockdep.c:3904 [inline] __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849 down_write+0x93/0x200 kernel/locking/rwsem.c:1577 inode_lock include/linux/fs.h:818 [inline] __generic_file_fsync+0xb0/0x1f0 fs/libfs.c:1536 fat_file_fsync+0x70/0x210 fs/fat/file.c:191 vfs_fsync_range fs/sync.c:187 [inline] vfs_fsync+0x12d/0x1f0 fs/sync.c:201 __loop_update_dio+0x182/0x570 drivers/block/loop.c:204 loop_set_status+0x2a4/0x700 drivers/block/loop.c:1289 loop_set_status64 drivers/block/loop.c:1398 [inline] lo_ioctl+0x6ec/0x18b0 drivers/block/loop.c:1548 blkdev_ioctl+0x279/0x6d0 block/ioctl.c:693 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl fs/ioctl.c:892 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 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#24 --> &sbi->fat_lock --> &q->q_usage_counter(io)#17 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#17); lock(&sbi->fat_lock); lock(&q->q_usage_counter(io)#17); lock(&sb->s_type->i_mutex_key#24); *** DEADLOCK *** 3 locks held by syz.3.565/7542: #0: ffff8880256acb60 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_set_status+0x2a/0x700 drivers/block/loop.c:1251 #1: ffff8880259e9e00 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: loop_set_status+0x1d9/0x700 drivers/block/loop.c:1267 #2: ffff8880259e9e38 (&q->q_usage_counter(queue)){+.+.}-{0:0}, at: loop_set_status+0x1d9/0x700 drivers/block/loop.c:1267 stack backtrace: CPU: 1 UID: 0 PID: 7542 Comm: syz.3.565 Not tainted 6.12.0-syzkaller-11930-g0e287d31b62b #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x419/0x5d0 kernel/locking/lockdep.c:2074 check_noncircular+0x31a/0x400 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 kernel/locking/lockdep.c:3904 [inline] __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849 down_write+0x93/0x200 kernel/locking/rwsem.c:1577 inode_lock include/linux/fs.h:818 [inline] __generic_file_fsync+0xb0/0x1f0 fs/libfs.c:1536 fat_file_fsync+0x70/0x210 fs/fat/file.c:191 vfs_fsync_range fs/sync.c:187 [inline] vfs_fsync+0x12d/0x1f0 fs/sync.c:201 __loop_update_dio+0x182/0x570 drivers/block/loop.c:204 loop_set_status+0x2a4/0x700 drivers/block/loop.c:1289 loop_set_status64 drivers/block/loop.c:1398 [inline] lo_ioctl+0x6ec/0x18b0 drivers/block/loop.c:1548 blkdev_ioctl+0x279/0x6d0 block/ioctl.c:693 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl fs/ioctl.c:892 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f0e45980849 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:00007f0e466d7058 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f0e45b45fa0 RCX: 00007f0e45980849 RDX: 0000000020001300 RSI: 0000000000004c04 RDI: 0000000000000004 RBP: 00007f0e459f3986 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f0e45b45fa0 R15: 00007ffee3dbe258