WARNING in request_end

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    6bf4ca7fbc85 Linux 4.19-rc5
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=159149c6400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=22a62640793a83c9
dashboard link: https://syzkaller.appspot.com/bug?extid=ef054c4d3f64cd7f7cec
compiler:       gcc (GCC) 8.0.1 20180413 (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+ef054c4d3f64cd7f7cec@xxxxxxxxxxxxxxxxxxxxxxxxx

WARNING: CPU: 0 PID: 9445 at fs/fuse/dev.c:390 request_end+0x82e/0xaa0  
fs/fuse/dev.c:390
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 9445 Comm: syz-executor2 Not tainted 4.19.0-rc5+ #251
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
kobject: '0:56' (00000000d57a9914): kobject_add_internal: parent: 'bdi',  
set: 'devices'
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
kobject: '0:56' (00000000d57a9914): kobject_uevent_env
 panic+0x238/0x4e7 kernel/panic.c:184
kobject: '0:56' (00000000d57a9914): fill_kobj_path: path  
= '/devices/virtual/bdi/0:56'
 __warn.cold.8+0x163/0x1ba kernel/panic.c:536
 report_bug+0x254/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x1fc/0x4d0 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:993
RIP: 0010:request_end+0x82e/0xaa0 fs/fuse/dev.c:390
Code: 3c 03 0f 8f 6f fe ff ff 48 8b bd f0 fe ff ff e8 68 e7 39 ff e9 5e fe  
ff ff e8 8e 86 f6 fe 0f 0b e9 b0 fa ff ff e8 82 86 f6 fe <0f> 0b e9 f0 fa  
ff ff e8 36 71 c0 fe e8 61 e7 39 ff e9 5b fb ff ff
RSP: 0018:ffff88019df0f378 EFLAGS: 00010212
RAX: 0000000000040000 RBX: ffff8801d2ca6000 RCX: ffffc90006d53000
RDX: 0000000000000138 RSI: ffffffff82885d9e RDI: 0000000000000007
RBP: ffff88019df0f4a8 R08: ffff8801d1a6c200 R09: ffffed0034b53937
R10: ffffed0034b53937 R11: ffff8801a5a9c9bb R12: 1ffff10033be1e74
R13: ffff8801a5a9c940 R14: ffff8801d2ca6030 R15: ffff88019df0f480
 fuse_dev_do_write+0x192e/0x36e0 fs/fuse/dev.c:1915
 fuse_dev_write+0x19a/0x240 fs/fuse/dev.c:1939
 call_write_iter include/linux/fs.h:1808 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x6b8/0x9f0 fs/read_write.c:487
 vfs_write+0x1fc/0x560 fs/read_write.c:549
 ksys_write+0x101/0x260 fs/read_write.c:598
 __do_sys_write fs/read_write.c:610 [inline]
 __se_sys_write fs/read_write.c:607 [inline]
 __x64_sys_write+0x73/0xb0 fs/read_write.c:607
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457679
Code: 1d b4 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 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007efd81affc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007efd81b006d4 RCX: 0000000000457679
RDX: 0000000000000090 RSI: 0000000020000500 RDI: 0000000000000003
RBP: 000000000072c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d8710 R14: 00000000004c50a2 R15: 0000000000000002
Kernel Offset: disabled
Rebooting in 86400 seconds..


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