[Bug 1880332] Re: Possible regression in QEMU 5.0.0 after CVE-2020-10702 (segmentation fault)

[Richard Henderson]

This is a compiler bug affecting (at least) libcrypto.so.1.1:

  179d90:       d503233f        paciasp
  179d94:       a9bb7bfd        stp     x29, x30, [sp, #-80]!
...
  17a400:       d50323bf        autiasp
  17a404:       f84507fd        ldr     x29, [sp], #80
  17a408:       d65f03c0        ret

The PAC happens with the initial sp:

  X30=0000005501de55fc  SP=00000055018477a0

while the AUTH happens with the decremented sp:

  X30=0011005501de55fc  SP=0000005501847750

Since the salt (sp) is different for the two operations, the
authorization should and does fail:

  X30=0020005501de55fc

Note bit 53 is now set in x30, which is the error indication.

The compiler must move the authiasp down below the ldr pop.


** Changed in: qemu
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1880332

Title:
  Possible regression in QEMU 5.0.0 after CVE-2020-10702 (segmentation
  fault)

Status in QEMU:
  Invalid

Bug description:
  I've come across a very specific situation, but I'm sure it could be
  replicated in other cases.

  In QEMU 5.0.0 when I use user emulation with a cURL binary for aarch64
  and connect to a server using TLS 1.2 and ECDHE-ECDSA-
  CHACHA20-POLY1305 cypher a segmentation fault occurs.

  I attach a Dockerfile that reproduces this crash and the strace output
  with and without the de0b1bae6461f67243282555475f88b2384a1eb9 commit
  reverted.

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