syzbot

kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN NOPTI
Modules linked in:
CPU: 0 PID: 9711 Comm: syz-executor1 Not tainted 4.14.93+ #6
task: ffff88819c9c1780 task.stack: ffff8881d5c70000
RIP: 0010:is_loop_device drivers/block/loop.c:622 [inline]
RIP: 0010:loop_validate_file+0x1ef/0x2c0 drivers/block/loop.c:633
RSP: 0018:ffff8881d5c77b60 EFLAGS: 00010202
RAX: 0000000000000037 RBX: ffff8881d9eadd98 RCX: 00000000000000b2
RDX: ffffffff81de1ff1 RSI: ffffc90002b74000 RDI: 00000000000001b8
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
R10: ffff88819c9c1fd8 R11: 0000000000000001 R12: ffff8881d9eacac0
R13: dffffc0000000000 R14: 00000000fffffff0 R15: ffff8881ce380780
FS:  00007f667400f700(0000) GS:ffff8881db800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001fa9978 CR3: 00000001cc4ec002 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 loop_set_fd drivers/block/loop.c:897 [inline]
 lo_ioctl+0x899/0x17e0 drivers/block/loop.c:1376
 __blkdev_driver_ioctl block/ioctl.c:297 [inline]
 blkdev_ioctl+0x4d9/0x1810 block/ioctl.c:594
 block_ioctl+0xd9/0x120 fs/block_dev.c:1873
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0xabe/0x1040 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
Code: f0 00 00 00 48 89 f8 48 c1 e8 03 42 80 3c 28 00 0f 85 d1 00 00 00 48 8b ad f0 00 00 00 48 8d bd b8 01 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 28 00 0f 85 a7 00 00 00 48 8b ad b8 01 00 00 48 89 e8 
RIP: is_loop_device drivers/block/loop.c:622 [inline] RSP: ffff8881d5c77b60
RIP: loop_validate_file+0x1ef/0x2c0 drivers/block/loop.c:633 RSP: ffff8881d5c77b60
---[ end trace 573e6e8079b7d656 ]---