631aebfee8
handle_sthyi() always writes to guest memory if the sthyi function
code is zero in order to fault in the page that later is written to.
However a function code of zero does not necessarily mean that a write
to guest memory happens: if the KVM host is running as a second level
guest under z/VM 6.2 the sthyi instruction is indicated to be
available to the KVM host, however if the instruction is executed it
will always return with a return code that indicates "unsupported
function code".
In such a case handle_sthyi() must not write to guest memory. This
means that the prior write access to fault in the guest page may
result in invalid guest exceptions, and/or invalid data modification.
In order to be architecture compliant simply remove the write_guest()
call.
Given that the guest assumed a write access anyway, this fix does not
qualify for -stable. This just makes sure the sthyi handler is
architecture compliant.
Fixes:
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|---|---|---|
| .. | ||
| appldata | ||
| boot | ||
| configs | ||
| crypto | ||
| hypfs | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| mm | ||
| net | ||
| numa | ||
| oprofile | ||
| pci | ||
| tools | ||
| defconfig | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||