[Xen-changelog] [xen master] grant_table: fix GNTTABOP_cache_flush handling

[patchbot@xxxxxxx]

commit c3d830b244998b3686e2eb64db95996be5eb5e5c
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Sep 12 14:44:11 2017 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Sep 12 14:44:11 2017 +0200

    grant_table: fix GNTTABOP_cache_flush handling
    
    Don't fall over a NULL grant_table pointer when the owner of the domain
    is a system domain (DOMID_{XEN,IO} etc).
    
    This is CVE-2017-14318 / XSA-232.
    
    Reported-by: Matthew Daley <mattd@xxxxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/grant_table.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index fb3859c..c3895e6 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -3046,7 +3046,7 @@ static int cache_flush(gnttab_cache_flush_t *cflush, 
grant_ref_t *cur_ref)
 
     page = mfn_to_page(mfn);
     owner = page_get_owner_and_reference(page);
-    if ( !owner )
+    if ( !owner || !owner->grant_table )
     {
         rcu_unlock_domain(d);
         return -EPERM;
--
generated by git-patchbot for /home/xen/git/xen.git#master

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