FAT-fs (loop3): error, invalid access to FAT (entry 0x0000616b)
======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc6-next-20241108-syzkaller #0 Not tainted
------------------------------------------------------
syz.3.2125/17744 is trying to acquire lock:
ffff8880691980b0 (&sbi->fat_lock){+.+.}-{4:4}, at: lock_fat fs/fat/fatent.c:281 [inline]
ffff8880691980b0 (&sbi->fat_lock){+.+.}-{4:4}, at: fat_count_free_clusters+0x156/0xe70 fs/fat/fatent.c:724
but task is already holding lock:
ffff88802533deb0 (&q->limits_lock){+.+.}-{4:4}, at: queue_limits_start_update include/linux/blkdev.h:944 [inline]
ffff88802533deb0 (&q->limits_lock){+.+.}-{4:4}, at: loop_reconfigure_limits+0x287/0x9f0 drivers/block/loop.c:1003
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&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:944 [inline]
loop_reconfigure_limits+0x287/0x9f0 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
-> #1 (&q->q_usage_counter(io)#17){++++}-{0:0}:
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:3095
__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_add_cluster fs/fat/inode.c:107 [inline]
__fat_get_block fs/fat/inode.c:154 [inline]
fat_get_block+0x4c4/0xd00 fs/fat/inode.c:189
__block_write_begin_int+0x50c/0x1a70 fs/buffer.c:2116
block_write_begin fs/buffer.c:2226 [inline]
cont_write_begin+0x6e2/0x9d0 fs/buffer.c:2577
fat_write_begin+0x76/0x140 fs/fat/inode.c:228
generic_perform_write+0x344/0x6d0 mm/filemap.c:4055
generic_file_write_iter+0xae/0x310 mm/filemap.c:4182
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0xaeb/0xd30 fs/read_write.c:679
ksys_write+0x18f/0x2b0 fs/read_write.c:731
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 (&sbi->fat_lock){+.+.}-{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
__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+0x5fe/0x9f0 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
other info that might help us debug this:
Chain exists of:
&sbi->fat_lock --> &q->q_usage_counter(io)#17 --> &q->limits_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&q->limits_lock);
lock(&q->q_usage_counter(io)#17);
lock(&q->limits_lock);
lock(&sbi->fat_lock);
*** DEADLOCK ***
2 locks held by syz.3.2125/17744:
#0: ffff88802541fb60 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable drivers/block/loop.c:120 [inline]
#0: ffff88802541fb60 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_configure+0x1f7/0xeb0 drivers/block/loop.c:1044
#1: ffff88802533deb0 (&q->limits_lock){+.+.}-{4:4}, at: queue_limits_start_update include/linux/blkdev.h:944 [inline]
#1: ffff88802533deb0 (&q->limits_lock){+.+.}-{4:4}, at: loop_reconfigure_limits+0x287/0x9f0 drivers/block/loop.c:1003
stack backtrace:
CPU: 0 UID: 0 PID: 17744 Comm: syz.3.2125 Not tainted 6.12.0-rc6-next-20241108-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
Call Trace:
<TASK>
__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
__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+0x5fe/0x9f0 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
RIP: 0033:0x7f9752d7e719
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:00007f9753abd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9752f36058 RCX: 00007f9752d7e719
RDX: 00000000200002c0 RSI: 0000000000004c0a RDI: 0000000000000008
RBP: 00007f9752df139e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9752f36058 R15: 00007ffe36e679e8
</TASK>