[Bug 1917184] [NEW] qemu-user vm86() segfaults handling interrupt with ss:sp in same page as cs:ip

[Jeffrey]

Public bug reported:

When using qemu-i386 to run a program that uses vm86(), if the vm86 code
calls an interrupt while cs:ip and ss:sp both point within the same
page, do_int tries to write to the page while it is not writable,
causing a segfault.

qemu version 5.2.0, x86-64 host.

** Affects: qemu
     Importance: Undecided
         Status: New

** Attachment added: "Example program"
   https://bugs.launchpad.net/bugs/1917184/+attachment/5469910/+files/vm86bug.c

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https://bugs.launchpad.net/bugs/1917184

Title:
  qemu-user vm86() segfaults handling interrupt with ss:sp in same page
  as cs:ip

Status in QEMU:
  New

Bug description:
  When using qemu-i386 to run a program that uses vm86(), if the vm86
  code calls an interrupt while cs:ip and ss:sp both point within the
  same page, do_int tries to write to the page while it is not writable,
  causing a segfault.

  qemu version 5.2.0, x86-64 host.

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