general protection fault in process_init_reply

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    1dcbe5f2c615 Add linux-next specific files for 20180717
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=148aac44400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ea5926dddb0db97a
dashboard link: https://syzkaller.appspot.com/bug?extid=b62f08f4d5857755e3bc
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=143725d0400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=120ef3b2400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b62f08f4d5857755e3bc@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
CPU: 0 PID: 17978 Comm: syz-executor367 Not tainted  
4.18.0-rc5-next-20180717+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:process_init_reply+0xedc/0x1500 fs/fuse/inode.c:923
Code: 0f 95 c0 84 c2 0f 85 65 05 00 00 49 8d be 00 01 00 00 80 8b e9 01 00  
00 06 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 32 05 00 00 49 c7 86 00 01 00 00 a0 7f 16 89 41
RSP: 0018:ffff8801a97cf478 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8801cdfdfb40 RCX: 0000000000000001
RDX: 0000000000000020 RSI: ffffffff826e5a3d RDI: 0000000000000100
RBP: ffff8801a97cf4b0 R08: ffff8801b2a625c0 R09: ffffed0039cd05da
R10: ffffed0039cd05da R11: ffff8801ce682ed3 R12: ffff8801ce682e00
R13: ffff8801cdfdfd29 R14: 0000000000000000 R15: ffff8801cdfdfd25
FS:  00007f7f6d9b8700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7f6d9d8e78 CR3: 00000001d64ed000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 request_end+0x3de/0xb20 fs/fuse/dev.c:402
 fuse_dev_do_read.isra.25+0xf21/0x1960 fs/fuse/dev.c:1316
 fuse_dev_read+0x1a9/0x250 fs/fuse/dev.c:1349
 call_read_iter include/linux/fs.h:1820 [inline]
 new_sync_read fs/read_write.c:406 [inline]
 __vfs_read+0x6ac/0x9b0 fs/read_write.c:418
 vfs_read+0x17f/0x3c0 fs/read_write.c:452
 ksys_read+0x101/0x260 fs/read_write.c:578
 __do_sys_read fs/read_write.c:588 [inline]
 __se_sys_read fs/read_write.c:586 [inline]
 __x64_sys_read+0x73/0xb0 fs/read_write.c:586
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445f69
Code: e8 ac e7 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 fb 0d fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f7f6d9b7da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00000000006dbc3c RCX: 0000000000445f69
RDX: 0000000000001000 RSI: 0000000020001000 RDI: 0000000000000006
RBP: 00000000006dbc38 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 64695f70756f7267 R14: 65646f6d746f6f72 R15: 0000000000000007
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace d538f9cc84504f57 ]---
RIP: 0010:process_init_reply+0xedc/0x1500 fs/fuse/inode.c:923
Code: 0f 95 c0 84 c2 0f 85 65 05 00 00 49 8d be 00 01 00 00 80 8b e9 01 00  
00 06 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 32 05 00 00 49 c7 86 00 01 00 00 a0 7f 16 89 41
RSP: 0018:ffff8801a97cf478 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8801cdfdfb40 RCX: 0000000000000001
RDX: 0000000000000020 RSI: ffffffff826e5a3d RDI: 0000000000000100
RBP: ffff8801a97cf4b0 R08: ffff8801b2a625c0 R09: ffffed0039cd05da
R10: ffffed0039cd05da R11: ffff8801ce682ed3 R12: ffff8801ce682e00
R13: ffff8801cdfdfd29 R14: 0000000000000000 R15: ffff8801cdfdfd25
FS:  00007f7f6d9b8700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7f6d9d8e78 CR3: 00000001d64ed000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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