bisecting fixing commit since c98875d930e915d01e8c40c7d3c16f00b3c8abe1
building syzkaller on b617407b25b37a7a8efa47127005d1f20dd0abe1
testing commit c98875d930e915d01e8c40c7d3c16f00b3c8abe1 with gcc (GCC) 8.1.0
kernel signature: 2a53c3af9960cc7308f079e645075afcaa338f3f
all runs: crashed: WARNING in loop_add
testing current HEAD c7ecf3e3a71c216327980f26b1e895ce9b07ad31
testing commit c7ecf3e3a71c216327980f26b1e895ce9b07ad31 with gcc (GCC) 8.1.0
kernel signature: 31fd3e89f3b1f5a1ade6aaba24be164771b3d433
all runs: crashed: WARNING in loop_add
revisions tested: 2, total time: 26m32.356442692s (build: 17m29.948487421s, test: 8m10.934990443s)
the crash still happens on HEAD
commit msg: Linux 4.19.92
crash: WARNING in loop_add
RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f13c8a956d4
R13: 00000000004c20ba R14: 00000000004d4988 R15: 0000000000000004
------------[ cut here ]------------
WARNING: CPU: 1 PID: 8344 at block/genhd.c:709 __device_add_disk.cold.31+0x97/0xe5 block/genhd.c:709
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 8344 Comm: syz-executor.4 Not tainted 4.19.92-syzkaller #0
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+0x123/0x177 lib/dump_stack.c:118
 panic+0x1cd/0x387 kernel/panic.c:186
 __warn.cold.8+0x1b/0x3c kernel/panic.c:541
 report_bug+0x1a4/0x200 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x200/0x350 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.31+0x97/0xe5 block/genhd.c:709
Code: fe eb e7 3c 03 7f 0c 48 8b bd 30 ff ff ff e8 f4 60 ac fe 8b 83 b8 05 00 00 e9 c5 d8 ff ff 48 c7 c7 a0 de fc 86 e8 bc 96 69 fe <0f> 0b e9 37 e2 ff ff 48 8d 73 0c 48 c7 c7 80 e5 fc 86 e8 a5 96 69
RSP: 0018:ffff8880a0b5fb10 EFLAGS: 00010282
RAX: 0000000000000024 RBX: ffff8880792b02c0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff888079a54940 RDI: ffffffff89a816a0
RBP: ffff8880a0b5fc10 R08: ffff888079a54960 R09: 0000000000000000
R10: 0000000000000000 R11: dffffc0000000000 R12: ffff8880792b0350
R13: ffff8880792b0918 R14: ffff8880792b02c4 R15: 0000000000000000
 device_add_disk+0xe/0x10 block/genhd.c:729
 add_disk include/linux/genhd.h:408 [inline]
 loop_add+0x595/0x7f0 drivers/block/loop.c:2025
 loop_control_ioctl+0x105/0x280 drivers/block/loop.c:2126
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x199/0x10d0 fs/ioctl.c:688
 ksys_ioctl+0x62/0x90 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710
 do_syscall_64+0xd6/0x4e0 arch/x86/entry/common.c:293
 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:00007f13c8a94c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f13c8a94c90 RCX: 0000000000458da9
RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f13c8a956d4
R13: 00000000004c20ba R14: 00000000004d4988 R15: 0000000000000004
Kernel Offset: disabled
Rebooting in 86400 seconds..