Hi all,

While fuzzing with trinity inside a KVM tools guest running the latest -next
kernel I've stumbled on the following spew:

[  306.065161] kernel tried to execute NX-protected page - exploit attempt? 
(uid: 0)
[  306.067295] BUG: unable to handle kernel paging request at ffff880053b8fd08
[  306.069237] IP: 0xffff880053b8fd08  (??:?)
[  306.070071] PGD 24b9c067 PUD 705dd2067 PMD 705d34067 PTE 8000000053b8f163
[  306.070071] Oops: 0011 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[  306.070071] Dumping ftrace buffer:
[  306.070071]    (ftrace buffer empty)
[  306.070071] Modules linked in:
[  306.070071] CPU: 16 PID: 9577 Comm: trinity-c194 Tainted: G        W     
3.15.0-rc8-next-20140605-sasha-00020-g833a807 #592
[  306.070071] task: ffff880053b90000 ti: ffff880053b8c000 task.ti: 
ffff880053b8c000
[  306.070071] RIP: 0xffff880053b8fd08  (??:?)
[  306.070071] RSP: 0018:ffff880053b8fcc8  EFLAGS: 00010287
[  306.070071] RAX: ffff8806286e8000 RBX: 0000000000000000 RCX: 0000004742e748d4
[  306.070071] RDX: 0000000000000007 RSI: ffffffff9fffd31c RDI: ffffffffa0558ed5
[  306.070071] RBP: ffff880053b8fd08 R08: 0000000000005d3c R09: 0000000000000000
[  306.070071] R10: 0000000000000000 R11: 0000000000000001 R12: ffff880053b8fdf8
[  306.070071] R13: ffff8803d55b8000 R14: ffff88065ea35cd0 R15: 0000000000000000
[  306.070071] FS:  00007f5c3bb31700(0000) GS:ffff8803d7000000(0000) 
knlGS:0000000000000000
[  306.070071] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  306.070071] CR2: ffff880053b8fd08 CR3: 0000000053b6b000 CR4: 00000000000006a0
[  306.070071] DR0: 00000000006d6000 DR1: 00000000006d6000 DR2: 0000000000000000
[  306.070071] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 000000000095060a
[  306.070071] Stack:
[  306.070071]  ffff880053b8fdc8 00000000026d7de0 0000000000000010 
7fffffffffffffff
[  306.070071]  0000000000000000 ffff88065ea35cd0 0000000000000001 
0000000000000000
[  306.095047]  ffff880053b8fda8 ffffffffa0000ad1 ffff8803d55b8000 
ffff8803d71d8340
[  306.095047] Call Trace:
[  306.095047] netlink_sendmsg (net/netlink/af_netlink.c:2398)
[  306.095047] sock_aio_write (net/socket.c:959 net/socket.c:974)
[  306.095047] ? sched_clock_local (kernel/sched/clock.c:214)
[  306.095047] ? vtime_account_user (kernel/sched/cputime.c:687)
[  306.095047] do_sync_write (fs/read_write.c:458)
[  306.095047] vfs_write (fs/read_write.c:534)
[  306.095047] SyS_write (fs/read_write.c:584 fs/read_write.c:576)
[  306.095047] tracesys (arch/x86/kernel/entry_64.S:542)
[ 306.095047] Code: 00 00 00 ff ff ff ff ff ff ff 7f 00 00 00 00 00 00 00 00 d0 
5c a3 5e 06 88 ff ff 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <a8> fd b8 
53 00 88 ff ff d1 0a 00 a0 ff ff ff ff 00 80 5b d5 03
All code
========
   0:   00 00                   add    %al,(%rax)
   2:   00 ff                   add    %bh,%bh
   4:   ff                      (bad)
   5:   ff                      (bad)
   6:   ff                      (bad)
   7:   ff                      (bad)
   8:   ff                      (bad)
   9:   ff                      (bad)
   a:   7f 00                   jg     0xc
   c:   00 00                   add    %al,(%rax)
   e:   00 00                   add    %al,(%rax)
  10:   00 00                   add    %al,(%rax)
  12:   00 d0                   add    %dl,%al
  14:   5c                      pop    %rsp
  15:   a3 5e 06 88 ff ff 01    movabs %eax,0x1ffff88065e
  1c:   00 00
        ...
  2a:*  00 a8 fd b8 53 00       add    %ch,0x53b8fd(%rax)               <-- 
trapping instruction
  30:   88 ff                   mov    %bh,%bh
  32:   ff d1                   callq  *%rcx
  34:   0a 00                   or     (%rax),%al
  36:   a0 ff ff ff ff 00 80    movabs 0xd55b8000ffffffff,%al
  3d:   5b d5
  3f:   03 00                   add    (%rax),%eax

Code starting with the faulting instruction
===========================================
   0:   a8 fd                   test   $0xfd,%al
   2:   b8 53 00 88 ff          mov    $0xff880053,%eax
   7:   ff d1                   callq  *%rcx
   9:   0a 00                   or     (%rax),%al
   b:   a0 ff ff ff ff 00 80    movabs 0xd55b8000ffffffff,%al
  12:   5b d5
  14:   03 00                   add    (%rax),%eax
[  306.095047] RIP 0xffff880053b8fd08  (??:?)
[  306.095047]  RSP <ffff880053b8fcc8>
[  306.095047] CR2: ffff880053b8fd08


Thanks,
Sasha
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