QEMU – NBD Server Long Export Name Stack Buffer Overflow

• Exploit Database
• 19 阅读

• 作者： Eric Blake
  日期： 2017-11-29
• 类别：

  • dos
  平台：

  • linux
• 来源：https://www.exploit-db.com/exploits/43194/

• Introduced in commit f37708f6b8 (2.10).The NBD spec says a client
  can request export names up to 4096 bytes in length, even though
  they should not expect success on names longer than 256.However,
  qemu hard-codes the limit of 256, and fails to filter out a client
  that probes for a longer name; the result is a stack smash that can
  potentially give an attacker arbitrary control over the qemu
  process.
  
  The smash can be easily demonstrated with this client:
  
  $ qemu-io f raw nbd://localhost:10809/$(printf %3000d 1 | tr ' ' a)
  
  If the qemu NBD server binary (whether the standalone qemu-nbd, or
  the builtin server of QMP nbd-server-start) was compiled with
  -fstack-protector-strong, the ability to exploit the stack smash
  into arbitrary execution is a lot more difficult (but still
  theoretically possible to a determined attacker, perhaps in
  combination with other CVEs).Still, crashing a running qemu (and
  losing the VM) is bad enough, even if the attacker did not obtain
  full execution control.