[syzbot] INFO: task hung in ext4_fill_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    f21b807c Merge tag 'drm-fixes-2021-06-11' of git://anongit..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=165fca57d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=30f476588412c065
dashboard link: https://syzkaller.appspot.com/bug?extid=c9ff4822a62eee994ea3
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17d19ce0300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=108d7988300000

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1646b8d0300000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1546b8d0300000
console output: https://syzkaller.appspot.com/x/log.txt?x=1146b8d0300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c9ff4822a62eee994ea3@xxxxxxxxxxxxxxxxxxxxxxxxx

INFO: task syz-executor768:8567 blocked for more than 143 seconds.
      Not tainted 5.13.0-rc5-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor768 state:D stack:27544 pid: 8567 ppid:  8423 flags:0x00004004
Call Trace:
 context_switch kernel/sched/core.c:4339 [inline]
 __schedule+0x916/0x23e0 kernel/sched/core.c:5147
 schedule+0xcf/0x270 kernel/sched/core.c:5226
 schedule_timeout+0x1db/0x250 kernel/time/timer.c:1868
 do_wait_for_common kernel/sched/completion.c:85 [inline]
 __wait_for_common kernel/sched/completion.c:106 [inline]
 wait_for_common kernel/sched/completion.c:117 [inline]
 wait_for_completion+0x168/0x270 kernel/sched/completion.c:138
 kthread_stop+0x17a/0x720 kernel/kthread.c:642
 ext4_fill_super+0x87ac/0xdfa0 fs/ext4/super.c:5190
 mount_bdev+0x34d/0x410 fs/super.c:1368
 legacy_get_tree+0x105/0x220 fs/fs_context.c:592
 vfs_get_tree+0x89/0x2f0 fs/super.c:1498
 do_new_mount fs/namespace.c:2905 [inline]
 path_mount+0x132a/0x1fa0 fs/namespace.c:3235
 do_mount fs/namespace.c:3248 [inline]
 __do_sys_mount fs/namespace.c:3456 [inline]
 __se_sys_mount fs/namespace.c:3433 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3433
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x445b2a
RSP: 002b:00007ffc5efbf598 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc5efbf5f0 RCX: 0000000000445b2a
RDX: 0000000020000000 RSI: 00000000200000c0 RDI: 00007ffc5efbf5b0
RBP: 00007ffc5efbf5b0 R08: 00007ffc5efbf5f0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00000000200003f8
R13: 0000000000000003 R14: 0000000000000004 R15: 0000000000000005

Showing all locks held in the system:
1 lock held by khungtaskd/1636:
 #0: ffffffff8bf79620 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6333
2 locks held by in:imklog/8117:
 #0: ffff888015be9770 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:974
 #1: ffff888021bc3958 (&mm->mmap_lock#2){++++}-{3:3}, at: file_ctx security/apparmor/include/file.h:33 [inline]
 #1: ffff888021bc3958 (&mm->mmap_lock#2){++++}-{3:3}, at: aa_file_perm+0x119/0x1170 security/apparmor/file.c:609
1 lock held by syz-executor768/8567:
 #0: ffff88802ac340e0 (&type->s_umount_key#27/1){+.+.}-{3:3}, at: alloc_super+0x1dd/0xab0 fs/super.c:229

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 1636 Comm: khungtaskd Not tainted 5.13.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline]
 watchdog+0xd48/0xfb0 kernel/hung_task.c:294
 kthread+0x3b1/0x4a0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:108 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x1c9/0x250 drivers/acpi/processor_idle.c:513


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
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