WARNING in __device_add_disk

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c98875d9 Linux 4.19.36
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16b38538a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=5e40ac5fbcc6366d
dashboard link: https://syzkaller.appspot.com/bug?extid=0615df2af2da6f1a069f
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+0615df...@syzkaller.appspotmail.com

R13: 00000000004c20ba R14: 00000000004d4988 R15: 0000000000000005
WARNING: CPU: 1 PID: 22062 at block/genhd.c:697
__device_add_disk+0xe63/0x10b0 block/genhd.c:697
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 22062 Comm: syz-executor.0 Not tainted 4.19.36 #4
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+0x263/0x51d kernel/panic.c:185
__warn.cold+0x20/0x54 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:997
RIP: 0010:__device_add_disk+0xe63/0x10b0 block/genhd.c:697
Code: ff ff 4c 89 e7 e8 bd 6c 8c fe e9 dc f2 ff ff e8 33 6d 8c fe e9 b7 f5
ff ff e8 39 0b 56 fe 0f 0b e9 92 fb ff ff e8 2d 0b 56 fe <0f> 0b e9 9a fe
ff ff e8 11 e0 29 fe 4c 89 f7 e8 c9 6c 8c fe e9 e1
RSP: 0018:ffff88805f387b08 EFLAGS: 00010246
RAX: 0000000000040000 RBX: ffff88805f387bf0 RCX: ffffc90006080000
RDX: 0000000000040000 RSI: ffffffff831539e3 RDI: 0000000000000005
RBP: ffff88805f387c18 R08: ffff88805d3f2140 R09: ffffed1015d24733
R10: ffffed1015d24732 R11: ffff8880ae923993 R12: ffff88805b02ac80
R13: ffff88805b02ad10 R14: 00000000fffffff4 R15: 0000000000000000
device_add_disk+0x23/0x30 block/genhd.c:717
add_disk include/linux/genhd.h:408 [inline]
loop_add+0x650/0x8d0 drivers/block/loop.c:2013
loop_control_ioctl drivers/block/loop.c:2114 [inline]
loop_control_ioctl+0x165/0x360 drivers/block/loop.c:2096
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xd6e/0x1390 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+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458da9
Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fcd0ebd6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fcd0ebd6c90 RCX: 0000000000458da9
RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fcd0ebd76d4
R13: 00000000004c20ba R14: 00000000004d4988 R15: 0000000000000005
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: c98875d9 Linux 4.19.36
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=12429acca00000

kernel config: https://syzkaller.appspot.com/x/.config?x=5e40ac5fbcc6366d
dashboard link: https://syzkaller.appspot.com/bug?extid=0615df2af2da6f1a069f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14b29660a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=116e0d38a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0615df...@syzkaller.appspotmail.com

RAX: ffffffffffffffda RBX: 00000000006dbc38 RCX: 00000000004468d9

RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003

RBP: 00000000006dbc30 R08: 0000000000000002 R09: 0000000000003035
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc3c
R13: 00007f666f179d90 R14: 0000000000000004 R15: 0000000000000007
WARNING: CPU: 1 PID: 12308 at block/genhd.c:697

__device_add_disk+0xe63/0x10b0 block/genhd.c:697
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 12308 Comm: syz-executor943 Not tainted 4.19.36 #4

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+0x263/0x51d kernel/panic.c:185
__warn.cold+0x20/0x54 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:997
RIP: 0010:__device_add_disk+0xe63/0x10b0 block/genhd.c:697
Code: ff ff 4c 89 e7 e8 bd 6c 8c fe e9 dc f2 ff ff e8 33 6d 8c fe e9 b7 f5
ff ff e8 39 0b 56 fe 0f 0b e9 92 fb ff ff e8 2d 0b 56 fe <0f> 0b e9 9a fe
ff ff e8 11 e0 29 fe 4c 89 f7 e8 c9 6c 8c fe e9 e1

RSP: 0018:ffff88809f7cfb08 EFLAGS: 00010293
RAX: ffff888095d30300 RBX: ffff88809f7cfbf0 RCX: ffffffff8315387b
RDX: 0000000000000000 RSI: ffffffff831539e3 RDI: 0000000000000005
RBP: ffff88809f7cfc18 R08: ffff888095d30300 R09: ffffed1015d24733
R10: ffffed1015d24732 R11: ffff8880ae923993 R12: ffff888096bd8580
R13: ffff888096bd8610 R14: 00000000fffffff4 R15: 0000000000000000

device_add_disk+0x23/0x30 block/genhd.c:717
add_disk include/linux/genhd.h:408 [inline]
loop_add+0x650/0x8d0 drivers/block/loop.c:2013
loop_control_ioctl drivers/block/loop.c:2114 [inline]
loop_control_ioctl+0x165/0x360 drivers/block/loop.c:2096
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xd6e/0x1390 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+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

RIP: 0033:0x4468d9
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:00007f666f179d88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dbc38 RCX: 00000000004468d9

RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003

RBP: 00000000006dbc30 R08: 0000000000000002 R09: 0000000000003035
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc3c
R13: 00007f666f179d90 R14: 0000000000000004 R15: 0000000000000007