On Sun, 03 Nov 2024 14:19:28 -0800 > syzbot found the following issue on: > > HEAD commit: f9f24ca362a4 Add linux-next specific files for 20241031 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=17f26630580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=328572ed4d152be9 > dashboard link: https://syzkaller.appspot.com/bug?extid=949ae54e95a2fab4cbb4 > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=102632a7980000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16749340580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/eb84549dd6b3/disk-f9f24ca3.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/beb29bdfa297/vmlinux-f9f24ca3.xz > kernel image: https://storage.googleapis.com/syzbot-assets/8881fe3245ad/bzImage-f9f24ca3.xz > mounted in repro: https://storage.googleapis.com/syzbot-assets/61af3e8f2dbd/mount_0.gz > > The issue was bisected to: > > commit f1be1788a32e8fa63416ad4518bbd1a85a825c9d > Author: Ming Lei <ming.lei@xxxxxxxxxx> > Date: Fri Oct 25 00:37:20 2024 +0000 > > block: model freeze & enter queue as lock for supporting lockdep > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13eafaa7980000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=101afaa7980000 > console output: https://syzkaller.appspot.com/x/log.txt?x=17eafaa7980000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+949ae54e95a2fab4cbb4@xxxxxxxxxxxxxxxxxxxxxxxxx > Fixes: f1be1788a32e ("block: model freeze & enter queue as lock for supporting lockdep") > > exFAT-fs (loop0): failed to load upcase table (idx : 0x00012153, chksum : 0x822ffc2e, utbl_chksum : 0xe619d30d) > ====================================================== > WARNING: possible circular locking dependency detected > 6.12.0-rc5-next-20241031-syzkaller #0 Not tainted > ------------------------------------------------------ > syz-executor382/6007 is trying to acquire lock: > ffff8881427474e8 (&q->q_usage_counter(io)#17){++++}-{0:0}, at: __submit_bio+0x2c2/0x560 block/blk-core.c:629 > > but task is already holding lock: > ffff888034dd00e8 (&sbi->s_lock){+.+.}-{4:4}, at: exfat_create+0x1a2/0x5a0 fs/exfat/namei.c:553 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #2 (&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 > exfat_lookup+0x140/0x18f0 fs/exfat/namei.c:701 > lookup_open fs/namei.c:3573 [inline] > open_last_lookups fs/namei.c:3694 [inline] > path_openat+0x11a7/0x3590 fs/namei.c:3930 > do_filp_open+0x235/0x490 fs/namei.c:3960 > do_sys_openat2+0x13e/0x1d0 fs/open.c:1419 > do_sys_open fs/open.c:1434 [inline] > __do_sys_openat fs/open.c:1450 [inline] > __se_sys_openat fs/open.c:1445 [inline] > __x64_sys_openat+0x247/0x2a0 fs/open.c:1445 > 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 (&sb->s_type->i_mutex_key#15){++++}-{4:4}: > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 > down_write+0x99/0x220 kernel/locking/rwsem.c:1577 > inode_lock include/linux/fs.h:817 [inline] > __generic_file_fsync+0x97/0x1a0 fs/libfs.c:1536 > exfat_file_fsync+0xf9/0x1d0 fs/exfat/file.c:524 > __loop_update_dio+0x1a4/0x500 drivers/block/loop.c:204 blk_mq_freeze_queue(lo->lo_queue); blk_freeze_queue_start(q); percpu_ref_kill(&q->q_usage_counter); blk_freeze_acquire_lock(q, false, false); blk_mq_freeze_queue_wait(q); wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter)); While waiting for the q_usage_counter to drop to zero, percpu_ref_tryget is allowed by the define of wait, so the acquire_read in bio_queue_enter() makes no sense. > loop_set_status+0x62b/0x8f0 drivers/block/loop.c:1290 > lo_ioctl+0xcbc/0x1f50 > blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:907 [inline] > __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893 > 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)#17){++++}-{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 static inline int bio_queue_enter(struct bio *bio) { struct request_queue *q = bdev_get_queue(bio->bi_bdev); if (blk_try_enter_queue(q, false)) { // // q_usage_counter is not zero otherwise // percpu_ref_tryget_live_rcu() failed // rwsem_acquire_read(&q->io_lockdep_map, 0, 0, _RET_IP_); rwsem_release(&q->io_lockdep_map, _RET_IP_); return 0; } return __bio_queue_enter(q, bio); } > 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] > __sync_dirty_buffer+0x23d/0x390 fs/buffer.c:2857 > exfat_set_volume_dirty+0x5d/0x80 fs/exfat/super.c:124 > exfat_create+0x1aa/0x5a0 fs/exfat/namei.c:554 > lookup_open fs/namei.c:3595 [inline] > open_last_lookups fs/namei.c:3694 [inline] > path_openat+0x1c03/0x3590 fs/namei.c:3930 > do_filp_open+0x235/0x490 fs/namei.c:3960 > do_sys_openat2+0x13e/0x1d0 fs/open.c:1419 > do_sys_open fs/open.c:1434 [inline] > __do_sys_openat fs/open.c:1450 [inline] > __se_sys_openat fs/open.c:1445 [inline] > __x64_sys_openat+0x247/0x2a0 fs/open.c:1445 > 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)#17 --> &sb->s_type->i_mutex_key#15 --> &sbi->s_lock > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&sbi->s_lock); > lock(&sb->s_type->i_mutex_key#15); > lock(&sbi->s_lock); > rlock(&q->q_usage_counter(io)#17); > > *** DEADLOCK *** > > 3 locks held by syz-executor382/6007: > #0: ffff888034b8a420 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:515 > #1: ffff88807733e330 (&sb->s_type->i_mutex_key#15){++++}-{4:4}, at: inode_lock include/linux/fs.h:817 [inline] > #1: ffff88807733e330 (&sb->s_type->i_mutex_key#15){++++}-{4:4}, at: open_last_lookups fs/namei.c:3691 [inline] > #1: ffff88807733e330 (&sb->s_type->i_mutex_key#15){++++}-{4:4}, at: path_openat+0x89a/0x3590 fs/namei.c:3930 > #2: ffff888034dd00e8 (&sbi->s_lock){+.+.}-{4:4}, at: exfat_create+0x1a2/0x5a0 fs/exfat/namei.c:553
