[Xen-changelog] [xen staging] x86/HVM: __hvm_copy() should not write to p2m_ioreq_server pages

[p***@xen.org]

commit d7bff2bc003cd5fd8c618b70c62b8fcfd9cd187e
Author: Jan Beulich <***@suse.com>
AuthorDate: Thu Nov 15 16:42:25 2018 +0100
Commit: Jan Beulich <***@suse.com>
CommitDate: Thu Nov 15 16:42:25 2018 +0100

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 <***@citrix.com>
Signed-off-by: Jan Beulich <***@suse.com>
Reviewed-by: Paul Durrant <***@citrix.com>
Acked-by: Andrew Cooper <***@citrix.com>
---
xen/arch/x86/hvm/hvm.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index c0a3db5858..65ab6a9b23 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3204,6 +3204,12 @@ 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 )
--
generated by git-patchbot for /home/xen/git/xen.git#staging