BUG: unable to handle kernel paging request in dput (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    02495e76ded5 Add linux-next specific files for 20190130
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17a5bb64c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a2b2e9c0bc43c14d
dashboard link: https://syzkaller.appspot.com/bug?extid=b382ba6a802a3d242790
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+b382ba6a802a3d242790@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: unable to handle kernel paging request at ffffffffffffffea
#PF error: [normal kernel read fault]
PGD 9874067 P4D 9874067 PUD 9876067 PMD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 18660 Comm: syz-executor2 Not tainted 5.0.0-rc4-next-20190130  
#22
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:fast_dput fs/dcache.c:700 [inline]
RIP: 0010:dput+0x11e/0x790 fs/dcache.c:819
Code: e8 97 2e a8 ff 45 84 ed 0f 84 e2 03 00 00 e8 49 2d a8 ff 4c 89 e0 48  
c1 e8 03 0f b6 04 18 84 c0 74 08 3c 03 0f 8e f7 04 00 00 <45> 8b 2c 24 4d  
8d bc 24 80 00 00 00 31 ff 41 83 e5 08 44 89 ee e8
RSP: 0018:ffff888050bef740 EFLAGS: 00010246
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffc9000c426000
RDX: 0000000000000777 RSI: ffffffff81d9ec07 RDI: 0000000000000001
RBP: ffff888050bef7d8 R08: ffff88805fc105c0 R09: ffffed1015ce5b80
R10: ffffed1015ce5b7f R11: ffff8880ae72dbfb R12: ffffffffffffffea
R13: 0000000000000001 R14: 1ffff1100a17deea R15: ffff888050bef8a0
FS:  00007f5052230700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffea CR3: 00000000a5276000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 do_blk_trace_setup+0x8e9/0xdb0 kernel/trace/blktrace.c:561
 __blk_trace_setup+0xe3/0x190 kernel/trace/blktrace.c:577
 blk_trace_ioctl+0x170/0x300 kernel/trace/blktrace.c:716
 blkdev_ioctl+0x141/0x2120 block/ioctl.c:591
 block_ioctl+0xee/0x130 fs/block_dev.c:1914
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458089
Code: 6d b7 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 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f505222fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458089
RDX: 00000000200002c0 RSI: 00000000c0481273 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f50522306d4
R13: 00000000004bf54d R14: 00000000004d0e38 R15: 00000000ffffffff
Modules linked in:
CR2: ffffffffffffffea
---[ end trace 454866349b9af1ed ]---
RIP: 0010:fast_dput fs/dcache.c:700 [inline]
RIP: 0010:dput+0x11e/0x790 fs/dcache.c:819
Code: e8 97 2e a8 ff 45 84 ed 0f 84 e2 03 00 00 e8 49 2d a8 ff 4c 89 e0 48  
c1 e8 03 0f b6 04 18 84 c0 74 08 3c 03 0f 8e f7 04 00 00 <45> 8b 2c 24 4d  
8d bc 24 80 00 00 00 31 ff 41 83 e5 08 44 89 ee e8
RSP: 0018:ffff888050bef740 EFLAGS: 00010246
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffc9000c426000
RDX: 0000000000000777 RSI: ffffffff81d9ec07 RDI: 0000000000000001
RBP: ffff888050bef7d8 R08: ffff88805fc105c0 R09: ffffed1015ce5b80
R10: ffffed1015ce5b7f R11: ffff8880ae72dbfb R12: ffffffffffffffea
R13: 0000000000000001 R14: 1ffff1100a17deea R15: ffff888050bef8a0
FS:  00007f5052230700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffea CR3: 00000000a5276000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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