WARNING in loop_add

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 893af1c7 Linux 4.19.66
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16a5d44c600000
kernel config: https://syzkaller.appspot.com/x/.config?x=d5fac5a8617b8643
dashboard link: https://syzkaller.appspot.com/bug?extid=82664f8405da365c7238
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+82664f...@syzkaller.appspotmail.com

R10: 0000000000000000 R11: 0000000000000246 R12: 00007f75931f26d4
R13: 00000000004c2f47 R14: 00000000004d6648 R15: 0000000000000006
------------[ cut here ]------------
WARNING: CPU: 1 PID: 22663 at block/genhd.c:709
__device_add_disk.cold+0x156/0x18d block/genhd.c:709
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 22663 Comm: syz-executor.4 Not tainted 4.19.66 #40
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+0x263/0x507 kernel/panic.c:185
__warn.cold+0x20/0x4a kernel/panic.c:540
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x204/0x360 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1037
RIP: 0010:__device_add_disk.cold+0x156/0x18d block/genhd.c:709
Code: 0f b6 04 02 84 c0 74 04 3c 03 7e 25 41 8b 9c 24 b8 05 00 00 e9 70 d2
ff ff e8 7a e3 54 fe 48 c7 c7 40 e4 80 87 e8 e2 4a 3f fe <0f> 0b e9 02 de
ff ff 48 8b bd 28 ff ff ff e8 5b 76 8b fe eb cd 48
RSP: 0018:ffff888059047b08 EFLAGS: 00010286
RAX: 0000000000000024 RBX: 00000000fffffff4 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8155d916 RDI: ffffed100b208f53
RBP: ffff888059047c18 R08: 0000000000000024 R09: ffffed1015d25079
R10: ffffed1015d25078 R11: ffff8880ae9283c7 R12: ffff888095e25400
R13: ffff888095e25490 R14: ffff888059047bf0 R15: ffff888095e25404
device_add_disk+0x23/0x30 block/genhd.c:729
add_disk include/linux/genhd.h:408 [inline]
loop_add+0x650/0x8d0 drivers/block/loop.c:2014
loop_control_ioctl drivers/block/loop.c:2115 [inline]
loop_control_ioctl+0x165/0x360 drivers/block/loop.c:2097
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:688
ksys_ioctl+0xab/0xd0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:710
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f75931f1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f75931f1c90 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f75931f26d4
R13: 00000000004c2f47 R14: 00000000004d6648 R15: 0000000000000006
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.
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[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 893af1c7 Linux 4.19.66
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=175b45ee600000

kernel config: https://syzkaller.appspot.com/x/.config?x=d5fac5a8617b8643
dashboard link: https://syzkaller.appspot.com/bug?extid=82664f8405da365c7238
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17387d72600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15308f1c600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+82664f...@syzkaller.appspotmail.com

RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 00000000006dbc30 R08: 0000000000000002 R09: 0000000000003934
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc3c
R13: 00007f9d13c33d90 R14: 0000000000000004 R15: 000000000000002d
------------[ cut here ]------------
WARNING: CPU: 0 PID: 12322 at block/genhd.c:709

__device_add_disk.cold+0x156/0x18d block/genhd.c:709
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 12322 Comm: syz-executor117 Not tainted 4.19.66 #40

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+0x263/0x507 kernel/panic.c:185
__warn.cold+0x20/0x4a kernel/panic.c:540
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x204/0x360 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1037
RIP: 0010:__device_add_disk.cold+0x156/0x18d block/genhd.c:709
Code: 0f b6 04 02 84 c0 74 04 3c 03 7e 25 41 8b 9c 24 b8 05 00 00 e9 70 d2
ff ff e8 7a e3 54 fe 48 c7 c7 40 e4 80 87 e8 e2 4a 3f fe <0f> 0b e9 02 de
ff ff 48 8b bd 28 ff ff ff e8 5b 76 8b fe eb cd 48

RSP: 0018:ffff8880967a7b08 EFLAGS: 00010286

RAX: 0000000000000024 RBX: 00000000fffffff4 RCX: 0000000000000000

RDX: 0000000000000000 RSI: ffffffff8155d916 RDI: ffffed1012cf4f53
RBP: ffff8880967a7c18 R08: 0000000000000024 R09: ffffed1015d05079
R10: ffffed1015d05078 R11: ffff8880ae8283c7 R12: ffff8880a47f8940
R13: ffff8880a47f89d0 R14: ffff8880967a7bf0 R15: ffff8880a47f8944

device_add_disk+0x23/0x30 block/genhd.c:729
add_disk include/linux/genhd.h:408 [inline]
loop_add+0x650/0x8d0 drivers/block/loop.c:2014
loop_control_ioctl drivers/block/loop.c:2115 [inline]
loop_control_ioctl+0x165/0x360 drivers/block/loop.c:2097
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:688
ksys_ioctl+0xab/0xd0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:710
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

RIP: 0033:0x4467f9
Code: e8 0c e8 ff ff 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 7b 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9d13c33d88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dbc38 RCX: 00000000004467f9
RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 00000000006dbc30 R08: 0000000000000002 R09: 0000000000003934
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc3c
R13: 00007f9d13c33d90 R14: 0000000000000004 R15: 000000000000002d