From: Jan Beulich <jbeulich@suse.com>
Date: Fri, 1 Feb 2019 10:27:59 +0000 (+0100)
Subject: x86/HVM: __hvm_copy() should not write to p2m_ioreq_server pages
X-Git-Tag: RELEASE-4.11.2~105
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=d8b2418573fb0c3f2a192620254d08826807d58a;p=people%2Fdwmw2%2Fxen.git

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>
master commit: d7bff2bc003cd5fd8c618b70c62b8fcfd9cd187e
master date: 2018-11-15 16:42:25 +0100
---

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 611545f898..2a34747a09 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3243,6 +3243,12 @@ static enum hvm_translation_result __hvm_copy(
         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 )