general protection fault in kobject_uevent_env

Hello,

syzbot found the following crash on:

HEAD commit: a74d0e93 Linux 4.14.126
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=149ff832a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=cb5b89703401900e
dashboard link: https://syzkaller.appspot.com/bug?extid=6331a4ebfc577a04f1e4
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: [email protected]

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: 7065 Comm: syz-executor.0 Not tainted 4.14.126 #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
task: ffff88809497a000 task.stack: ffff88808cd60000
RIP: 0010:kobject_uevent_env+0xa1/0xc23 lib/kobject_uevent.c:350
RSP: 0018:ffff88808cd67b60 EFLAGS: 00010286
RAX: dffffc0000000000 RBX: 0000000000000002 RCX: 1ffff1101292f50e
RDX: 0000000000000014 RSI: 0000000000000002 RDI: ffffffff870751f0
RBP: ffff88808cd67be0 R08: ffff88809497a000 R09: 0000000000000003
R10: 0000000000000000 R11: ffff88809497a000 R12: 00000000000000a0
R13: 0000000000000002 R14: ffff88805bba4380 R15: 00000000000000a0
FS: 0000000001f76940(0000) GS:ffff8880aef00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc614cb2000 CR3: 0000000094b38000 CR4: 00000000001406e0
Call Trace:
kobject_uevent+0x20/0x26 lib/kobject_uevent.c:553
loop_clr_fd+0x4a7/0xae0 drivers/block/loop.c:1059
__lo_release drivers/block/loop.c:1649 [inline]
lo_release+0x112/0x1b0 drivers/block/loop.c:1667
__blkdev_put+0x434/0x7f0 fs/block_dev.c:1791
blkdev_put+0x88/0x510 fs/block_dev.c:1856
kill_block_super+0xbd/0xf0 fs/super.c:1164
deactivate_locked_super+0x74/0xe0 fs/super.c:319
deactivate_super fs/super.c:350 [inline]
deactivate_super+0x85/0xa0 fs/super.c:346
cleanup_mnt+0xb2/0x150 fs/namespace.c:1183
__cleanup_mnt+0x16/0x20 fs/namespace.c:1190
task_work_run+0x114/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1da/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+0x4bc/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45bcf7
RSP: 002b:00007fffa4efa438 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000045bcf7
RDX: 00000000004036a0 RSI: 0000000000000002 RDI: 00007fffa4efa4e0
RBP: 0000000000000aa0 R08: 0000000000000000 R09: 000000000000000b
R10: 0000000000000005 R11: 0000000000000206 R12: 00007fffa4efb570
R13: 0000000001f77940 R14: 0000000000000000 R15: 00007fffa4efb570
Code: fa 83 e2 07 38 d0 7f 09 84 c0 74 05 e8 1f bf 70 fb 41 80 4f 3c 08 e8
45 1e 47 fb 4c 89 fa b8 ff ff 37 00 48 c1 ea 03 48 c1 e0 2a <80> 3c 02 00
74 08 4c 89 ff e8 b7 be 70 fb 49 8b 37 48 c7 c1 e0
RIP: kobject_uevent_env+0xa1/0xc23 lib/kobject_uevent.c:350 RSP:
ffff88808cd67b60
---[ end trace 08862c74f4de2909 ]---


---
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syzbot has found a reproducer for the following crash on:

HEAD commit: f4cc0ed9 Linux 4.14.131
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10f8a5d5a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=ab1953b2cdac00f5
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12151dd5a00000
CPU: 1 PID: 9795 Comm: syz-executor.0 Not tainted 4.14.131 #25
task: ffff88808541c300 task.stack: ffff8880a0888000
RSP: 0018:ffff8880a088fb60 EFLAGS: 00010286
RAX: dffffc0000000000 RBX: 0000000000000002 RCX: 1ffff11010a8396e
RDX: 0000000000000014 RSI: 0000000000000002 RDI: ffffffff870758b0
RBP: ffff8880a088fbe0 R08: ffff88808541c300 R09: 0000000000000003
R10: 0000000000000000 R11: ffff88808541c300 R12: 00000000000000a0
R13: 0000000000000002 R14: ffff88809002e7c0 R15: 00000000000000a0
FS: 00007f8c6d42b700(0000) GS:ffff8880aef00000(0000) knlGS:0000000000000000
CR2: 0000000002258008 CR3: 00000000a48e3000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
blkdev_close+0x8b/0xb0 fs/block_dev.c:1863
__fput+0x275/0x7a0 fs/file_table.c:210
____fput+0x16/0x20 fs/file_table.c:244
RIP: 0033:0x4134b1
RSP: 002b:00007f8c6d42aa80 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00007f8c6d42b6d4 RCX: 00000000004134b1
RDX: 0000000000000003 RSI: 0000000000004c00 RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000293 R12: 0000000000000003
R13: 00000000004c8878 R14: 00000000004df488 R15: 00000000ffffffff
Code: fa 83 e2 07 38 d0 7f 09 84 c0 74 05 e8 0f 9b 70 fb 41 80 4f 3c 08 e8
15 f9 46 fb 4c 89 fa b8 ff ff 37 00 48 c1 ea 03 48 c1 e0 2a <80> 3c 02 00
74 08 4c 89 ff e8 a7 9a 70 fb 49 8b 37 48 c7 c1 a0
ffff8880a088fb60
---[ end trace d64cf6038a87b7ba ]---