Date:   Fri, 19 Jan 2018 13:58:01 -0800
From:   syzbot <syzbot+5dfdbcf7b3eb5912abbb@...kaller.appspotmail.com>
To:     anna.schumaker@...app.com, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        trond.myklebust@...marydata.com
Subject: general protection fault in nfs_idmap_legacy_upcall

Hello,

syzbot hit the following crash on upstream commit
dda3e15231b35840fe6f0973f803cc70ddb86281 (Thu Jan 18 18:57:59 2018 +0000)
Merge branch 'fixes' of git://git.armlinux.org.uk/~rmk/linux-arm

So far this crash happened 4 times on linux-next, mmots, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5dfdbcf7b3eb5912abbb@...kaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

audit: type=1400 audit(1516307868.273:7): avc:  denied  { map } for   
pid=3665 comm="syzkaller312387" path="/root/syzkaller312387249" dev="sda1"  
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
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
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3665 Comm: syzkaller312387 Not tainted 4.15.0-rc8+ #268
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:nfs_idmap_prepare_pipe_upcall fs/nfs/nfs4idmap.c:537 [inline]
RIP: 0010:nfs_idmap_legacy_upcall+0x290/0x4f0 fs/nfs/nfs4idmap.c:588
RSP: 0018:ffff8801d952fbd0 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 1ffff1003b2a5f7c RCX: ffffffff82083117
RDX: 0000000000000005 RSI: 1ffff1003b2f0953 RDI: 0000000000000028
RBP: ffff8801d952fc68 R08: 1ffff1003b2a5f29 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801d964cd00 R14: 1ffff1003b2a5f80 R15: ffff8801d97311c0
FS:  0000000002467880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020006000 CR3: 00000001d97c4001 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  construct_key security/keys/request_key.c:235 [inline]
  construct_key_and_link security/keys/request_key.c:484 [inline]
  request_key_and_link+0x10fd/0x16c0 security/keys/request_key.c:593
  SYSC_request_key security/keys/keyctl.c:213 [inline]
  SyS_request_key+0x18c/0x2d0 security/keys/keyctl.c:158
  entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x43fce9
RSP: 002b:00007ffc405e62e8 EFLAGS: 00000217 ORIG_RAX: 00000000000000f9
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fce9
RDX: 0000000020000000 RSI: 0000000020000000 RDI: 0000000020005ff6
RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000fffffffe R11: 0000000000000217 R12: 0000000000401610
R13: 00000000004016a0 R14: 0000000000000000 R15: 0000000000000000
Code: 89 85 68 ff ff ff 66 41 89 14 06 78 47 e8 79 f9 67 ff 48 8b 85 70 ff  
ff ff 48 8d 78 28 48 8b 85 68 ff ff ff 48 89 fa 48 c1 ea 03 <80> 3c 02 00  
0f 85 39 02 00 00 48 8b 85 70 ff ff ff 48 83 78 28
RIP: nfs_idmap_prepare_pipe_upcall fs/nfs/nfs4idmap.c:537 [inline] RSP:  
ffff8801d952fbd0
RIP: nfs_idmap_legacy_upcall+0x290/0x4f0 fs/nfs/nfs4idmap.c:588 RSP:  
ffff8801d952fbd0
---[ end trace 4ab6ef81564187ba ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
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View attachment "raw.log.txt" of type "text/plain" (4675 bytes)

View attachment "repro.syz.txt" of type "text/plain" (510 bytes)

View attachment "repro.c.txt" of type "text/plain" (630 bytes)

View attachment "config.txt" of type "text/plain" (135111 bytes)

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