Subject: general protection fault in p9_client_prepare_req

From: syzbot <[email-masked]>
Date: Thu, 19 Jul 2018 05:09:02 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    1c34981993da Add linux-next specific files for 20180719
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=160ec658400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7002497517b09aec
dashboard link: https://syzkaller.appspot.com/bug?extid=77a28a63a0ece0fbba97
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=17317a58400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1135e1c2400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

RBP: 0000000000000000 R08: 0000000020000840 R09: 0000000000003831
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc432a9cd0
R13: 0030656c69662f2e R14: 64663d736e617274 R15: 0000000000000006
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: 1 PID: 4386 Comm: syz-executor227 Not tainted  
4.18.0-rc5-next-20180719+ #11
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:p9_client_prepare_req.part.8+0x392/0xa00 net/9p/client.c:645
Code: ff 0f 87 6a 02 00 00 e8 bc 39 0c fa 0f be 85 f4 fe ff ff 4c 89 f2 48  
c1 ea 03 89 85 f4 fe ff ff 48 b8 00 00 00 00 00 fc ff df <80> 3c 02 00 0f  
85 89 05 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b
RSP: 0018:ffff8801bd8c7250 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000600040
RDX: 000000000000000a RSI: ffffffff87706d04 RDI: ffff8801b9efa378
RBP: ffff8801bd8c7380 R08: ffff8801b9f24080 R09: ffffed0037b18de4
R10: ffffed0037b18de4 R11: 0000000000000003 R12: ffff8801b9efa340
R13: 0000000000002000 R14: 0000000000000050 R15: ffff8801b9efa37c
FS:  0000000001ba1880(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000200 CR3: 00000001b994e000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  p9_client_prepare_req net/9p/client.c:675 [inline]
  p9_client_rpc+0x242/0x1330 net/9p/client.c:675
  p9_client_version net/9p/client.c:890 [inline]
  p9_client_create+0xca4/0x1537 net/9p/client.c:974
  v9fs_session_init+0x21a/0x1a80 fs/9p/v9fs.c:400
  v9fs_mount+0x7c/0x900 fs/9p/vfs_super.c:135
  legacy_get_tree+0x131/0x460 fs/fs_context.c:674
  vfs_get_tree+0x1cb/0x5c0 fs/super.c:1743
  do_new_mount fs/namespace.c:2603 [inline]
  do_mount+0x6f2/0x1e20 fs/namespace.c:2927
  ksys_mount+0x12d/0x140 fs/namespace.c:3143
  __do_sys_mount fs/namespace.c:3157 [inline]
  __se_sys_mount fs/namespace.c:3154 [inline]
  __x64_sys_mount+0xbe/0x150 fs/namespace.c:3154
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440719
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc432a9cc8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000440719
RDX: 0000000020000900 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000020000840 R09: 0000000000003831
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc432a9cd0
R13: 0030656c69662f2e R14: 64663d736e617274 R15: 0000000000000006
Modules linked in:
Dumping ftrace buffer:
    (ftrace buffer empty)
---[ end trace bae3d5802518770f ]---
RIP: 0010:p9_client_prepare_req.part.8+0x392/0xa00 net/9p/client.c:645
Code: ff 0f 87 6a 02 00 00 e8 bc 39 0c fa 0f be 85 f4 fe ff ff 4c 89 f2 48  
c1 ea 03 89 85 f4 fe ff ff 48 b8 00 00 00 00 00 fc ff df <80> 3c 02 00 0f  
85 89 05 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b
RSP: 0018:ffff8801bd8c7250 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000600040
RDX: 000000000000000a RSI: ffffffff87706d04 RDI: ffff8801b9efa378
RBP: ffff8801bd8c7380 R08: ffff8801b9f24080 R09: ffffed0037b18de4
R10: ffffed0037b18de4 R11: 0000000000000003 R12: ffff8801b9efa340
R13: 0000000000002000 R14: 0000000000000050 R15: ffff8801b9efa37c
FS:  0000000001ba1880(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000200 CR3: 00000001b994e000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email-masked].

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches