File 5bed93e1-x86-hvm_copy-no-write-to-p2m_ioreq_server.patch of Package xen.9798

# Commit d7bff2bc003cd5fd8c618b70c62b8fcfd9cd187e
# Date 2018-11-15 16:42:25 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
x86/HVM: __hvm_copy() should not write to p2m_ioreq_server pages

Commit 3bdec530a5 ("x86/HVM: split page straddling emulated accesses in
more cases") introduced a hvm_copy_to_guest_linear() attempt before
falling back to hvmemul_linear_mmio_write(). This is wrong for the
p2m_ioreq_server special case. That change widened a pre-existing issue
though: Other writes to such pages also need to be failed (or forced
through emulation), in particular hypercall buffer writes.

Reported-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3237,6 +3237,12 @@ static enum hvm_translation_result __hvm
         if ( res != HVMTRANS_okay )
             return res;
 
+        if ( (flags & HVMCOPY_to_guest) && p2mt == p2m_ioreq_server )
+        {
+            put_page(page);
+            return HVMTRANS_bad_gfn_to_mfn;
+        }
+
         p = (char *)__map_domain_page(page) + (addr & ~PAGE_MASK);
 
         if ( flags & HVMCOPY_to_guest )