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

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.