loop7: detected capacity change from 0 to 256 ====================================================== WARNING: possible circular locking dependency detected 6.12.0-rc6-next-20241105-syzkaller #0 Not tainted ------------------------------------------------------ syz.7.2834/21819 is trying to acquire lock: ffff8880255f61d8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: __submit_bio+0x2c2/0x560 block/blk-core.c:629 but task is already holding lock: ffff88806a6100b0 (&sbi->fat_lock){+.+.}-{4:4}, at: lock_fat fs/fat/fatent.c:281 [inline] ffff88806a6100b0 (&sbi->fat_lock){+.+.}-{4:4}, at: fat_alloc_clusters+0x1a7/0x11c0 fs/fat/fatent.c:477 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&sbi->fat_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 lock_fat fs/fat/fatent.c:281 [inline] fat_count_free_clusters+0x156/0xe70 fs/fat/fatent.c:724 fat_statfs+0x139/0x450 fs/fat/inode.c:834 statfs_by_dentry fs/statfs.c:66 [inline] vfs_statfs+0x13b/0x2c0 fs/statfs.c:90 loop_config_discard drivers/block/loop.c:798 [inline] loop_reconfigure_limits+0x5f8/0x9e0 drivers/block/loop.c:1012 loop_configure+0x77e/0xeb0 drivers/block/loop.c:1093 lo_ioctl+0x846/0x1f50 blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf5/0x170 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 -> #1 (&q->limits_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 queue_limits_start_update include/linux/blkdev.h:941 [inline] loop_reconfigure_limits+0x281/0x9e0 drivers/block/loop.c:1003 loop_set_block_size drivers/block/loop.c:1473 [inline] lo_simple_ioctl drivers/block/loop.c:1496 [inline] lo_ioctl+0x1351/0x1f50 drivers/block/loop.c:1559 blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf5/0x170 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 -> #0 (&q->q_usage_counter(io)#24){++++}-{0:0}: 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 bio_queue_enter block/blk.h:75 [inline] blk_mq_submit_bio+0x1510/0x2490 block/blk-mq.c:3069 __submit_bio+0x2c2/0x560 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] __bread_slow fs/buffer.c:1264 [inline] __bread_gfp+0x23c/0x400 fs/buffer.c:1488 sb_bread include/linux/buffer_head.h:346 [inline] fat12_ent_bread+0x155/0x540 fs/fat/fatent.c:77 fat_ent_read_block+0x3e4/0x530 fs/fat/fatent.c:445 fat_alloc_clusters+0x4ee/0x11c0 fs/fat/fatent.c:493 fat_alloc_new_dir+0x1a1/0xe60 fs/fat/dir.c:1156 vfat_mkdir+0x169/0x330 fs/fat/namei_vfat.c:859 vfs_mkdir+0x2f9/0x4f0 fs/namei.c:4311 do_mkdirat+0x264/0x3a0 fs/namei.c:4334 __do_sys_mkdirat fs/namei.c:4349 [inline] __se_sys_mkdirat fs/namei.c:4347 [inline] __x64_sys_mkdirat+0x87/0xa0 fs/namei.c:4347 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: &q->q_usage_counter(io)#24 --> &q->limits_lock --> &sbi->fat_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sbi->fat_lock); lock(&q->limits_lock); lock(&sbi->fat_lock); rlock(&q->q_usage_counter(io)#24); *** DEADLOCK *** 4 locks held by syz.7.2834/21819: #0: ffff88806fe92420 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:515 #1: ffff8880604e3b10 (&sb->s_type->i_mutex_key#21/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:852 [inline] #1: ffff8880604e3b10 (&sb->s_type->i_mutex_key#21/1){+.+.}-{4:4}, at: filename_create+0x260/0x540 fs/namei.c:4080 #2: ffff88806a6101d0 (&sbi->s_lock#2){+.+.}-{4:4}, at: vfat_mkdir+0xf8/0x330 fs/fat/namei_vfat.c:856 #3: ffff88806a6100b0 (&sbi->fat_lock){+.+.}-{4:4}, at: lock_fat fs/fat/fatent.c:281 [inline] #3: ffff88806a6100b0 (&sbi->fat_lock){+.+.}-{4:4}, at: fat_alloc_clusters+0x1a7/0x11c0 fs/fat/fatent.c:477 stack backtrace: CPU: 1 UID: 0 PID: 21819 Comm: syz.7.2834 Not tainted 6.12.0-rc6-next-20241105-syzkaller #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+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 bio_queue_enter block/blk.h:75 [inline] blk_mq_submit_bio+0x1510/0x2490 block/blk-mq.c:3069 __submit_bio+0x2c2/0x560 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] __bread_slow fs/buffer.c:1264 [inline] __bread_gfp+0x23c/0x400 fs/buffer.c:1488 sb_bread include/linux/buffer_head.h:346 [inline] fat12_ent_bread+0x155/0x540 fs/fat/fatent.c:77 fat_ent_read_block+0x3e4/0x530 fs/fat/fatent.c:445 fat_alloc_clusters+0x4ee/0x11c0 fs/fat/fatent.c:493 fat_alloc_new_dir+0x1a1/0xe60 fs/fat/dir.c:1156 vfat_mkdir+0x169/0x330 fs/fat/namei_vfat.c:859 vfs_mkdir+0x2f9/0x4f0 fs/namei.c:4311 do_mkdirat+0x264/0x3a0 fs/namei.c:4334 __do_sys_mkdirat fs/namei.c:4349 [inline] __se_sys_mkdirat fs/namei.c:4347 [inline] __x64_sys_mkdirat+0x87/0xa0 fs/namei.c:4347 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: 0033:0x7f45ad37e719 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:00007f45ae13b038 EFLAGS: 00000246 ORIG_RAX: 0000000000000102 RAX: ffffffffffffffda RBX: 00007f45ad535f80 RCX: 00007f45ad37e719 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: ffffffffffffff9c RBP: 00007f45ad3f139e R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f45ad535f80 R15: 00007ffd60040d08