WARNING in loop_add

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: bb7ba806 Merge tag 'for-linus' of git://git.kernel.org/pub..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1272e012600000
kernel config: https://syzkaller.appspot.com/x/.config?x=6919752cc1b760b4
dashboard link: https://syzkaller.appspot.com/bug?extid=f41893bb8c45cd18cf08
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12aa5af2600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173eea1e600000

The bug was bisected to:

commit e41d58185f1444368873d4d7422f7664a68be61d
Author: Dmitry Vyukov <dvy...@google.com>
Date: Wed Jul 12 21:34:35 2017 +0000

fault-inject: support systematic fault injection

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12979da6600000
final crash: https://syzkaller.appspot.com/x/report.txt?x=11979da6600000
console output: https://syzkaller.appspot.com/x/log.txt?x=16979da6600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f41893...@syzkaller.appspotmail.com
Fixes: e41d58185f14 ("fault-inject: support systematic fault injection")

RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 00007fff862aa420 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
R13: 0000000000000005 R14: 0000000000000000 R15: 0000000000000000
------------[ cut here ]------------
WARNING: CPU: 0 PID: 10346 at block/genhd.c:732
__device_add_disk.cold+0x11/0x19e block/genhd.c:732
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 10346 Comm: syz-executor227 Not tainted 5.3.0-rc5+ #139
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
panic+0x2dc/0x755 kernel/panic.c:219
__warn.cold+0x20/0x4c kernel/panic.c:576
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:179 [inline]
fixup_bug arch/x86/kernel/traps.c:174 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:__device_add_disk.cold+0x11/0x19e block/genhd.c:732
Code: 41 bc f0 ff ff ff e8 ff c7 2c fe 48 8b 7d d0 e8 52 ed 7c fe e9 ba 7a
ff ff e8 18 27 43 fe 48 c7 c7 40 c5 c4 87 e8 e0 c7 2c fe <0f> 0b e9 7b de
ff ff e8 00 27 43 fe 48 c7 c7 40 c5 c4 87 e8 c8 c7
RSP: 0018:ffff88808899faf8 EFLAGS: 00010286
RAX: 0000000000000024 RBX: 00000000fffffff4 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815c2526 RDI: ffffed1011133f51
RBP: ffff88808899fc10 R08: 0000000000000024 R09: ffffed1015d060d1
R10: ffffed1015d060d0 R11: ffff8880ae830687 R12: ffff8880a9a895c0
R13: ffff8880a9a89650 R14: ffff88808899fbe8 R15: ffff8880a9a895c4
device_add_disk+0x2b/0x40 block/genhd.c:754
add_disk include/linux/genhd.h:429 [inline]
loop_add+0x635/0x8d0 drivers/block/loop.c:2050
loop_control_ioctl drivers/block/loop.c:2151 [inline]
loop_control_ioctl+0x165/0x360 drivers/block/loop.c:2133
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441319
Code: e8 5c ae 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 bb 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff862aa408 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441319
RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 00007fff862aa420 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
R13: 0000000000000005 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug 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 syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches