Hello, syzbot found the following issue on: HEAD commit: 929beafbe7ac Add linux-next specific files for 20241108 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1621bd87980000 kernel config: https://syzkaller.appspot.com/x/.config?x=75175323f2078363 dashboard link: https://syzkaller.appspot.com/bug?extid=a5d8c609c02f508672cc compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/9705ecb6a595/disk-929beafb.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/dbdd1f64b9b8/vmlinux-929beafb.xz kernel image: https://storage.googleapis.com/syzbot-assets/3f70d07a929b/bzImage-929beafb.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+a5d8c609c02f508672cc@xxxxxxxxxxxxxxxxxxxxxxxxx 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> --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup
