general protection fault in loop_clr_fd

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 78d697fc Linux 4.14.172
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10040075e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=3484a1ea90b8523a
dashboard link: https://syzkaller.appspot.com/bug?extid=c9f035f0754fe495fc84
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c9f035...@syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 19222 Comm: syz-executor.1 Not tainted 4.14.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88809946c440 task.stack: ffff88807fdb8000
RIP: 0010:kobject_uevent_env+0xa3/0xc50 lib/kobject_uevent.c:355
RSP: 0018:ffff88807fdbfc18 EFLAGS: 00010206
RAX: 0000000000000018 RBX: 0000000000000002 RCX: 1ffff1101328d996
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00000000000000c0
RBP: ffff8880a7862b50 R08: 0000000000000001 R09: 0000000000000003
R10: ffff88809946cd38 R11: ffff88809946c440 R12: 00000000000000a0
R13: dffffc0000000000 R14: ffff8880a7862a48 R15: 00000000000000a0
FS: 00000000012b0940(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fb3e000 CR3: 000000008d6a4000 CR4: 00000000001426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
loop_clr_fd+0x49e/0xad0 drivers/block/loop.c:1069
__lo_release drivers/block/loop.c:1660 [inline]
lo_release+0xff/0x190 drivers/block/loop.c:1678
__blkdev_put+0x4ec/0x6a0 fs/block_dev.c:1791
blkdev_close+0x86/0xb0 fs/block_dev.c:1863
__fput+0x25f/0x790 fs/file_table.c:210
task_work_run+0x113/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1d6/0x220 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x416261
RSP: 002b:00007ffffca9e690 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000009 RCX: 0000000000416261
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 0000000000000001 R08: ffffffff8129ba9c R09: 00000000f2dc4e0b
R10: 00007ffffca9e770 R11: 0000000000000293 R12: 000000000076bf20
R13: 0000000000771ab8 R14: 000000000009635e R15: 000000000076bf2c
Code: 03 42 80 3c 28 00 0f 85 2e 0a 00 00 4d 8b 64 24 18 4d 85 e4 0f 84 1e 02 00 00 e8 f9 f9 1f fb 49 8d 7c 24 20 48 89 f8 48 c1 e8 03 <42> 80 3c 28 00 0f 85 fa 09 00 00 49 8b 6c 24 20 48 85 ed 74 b0
RIP: kobject_uevent_env+0xa3/0xc50 lib/kobject_uevent.c:355 RSP: ffff88807fdbfc18
---[ end trace ccbfe35027f972f2 ]---


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.