[Xen-changelog] [xen stable-4.5] gnttab: correct maptrack table access

[patchbot@xxxxxxx]

commit c5de05e82fc0e6d2159fd3ff97d26f5516542a08
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Jun 20 16:52:39 2017 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jun 20 16:52:39 2017 +0200

    gnttab: correct maptrack table access
    
    In order to observe a consistent (limit,pointer-table) pair, the reader
    needs to either hold the grant table lock or both sides need to order
    their accesses suitably (the writer side barrier is already there). Add
    the missing barrier.
    
    This is part of XSA-218.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    master commit: 4b78efa91c8ae3c42e14b8eaeaad773c5eb3b71a
    master date: 2017-06-20 14:34:34 +0200
---
 xen/common/grant_table.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 5203929..ac98aef 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -908,7 +908,9 @@ __gnttab_unmap_common(
         return;
     }
 
+    smp_rmb();
     map = &maptrack_entry(lgt, op->handle);
+
     spin_lock(&lgt->lock);
 
     if ( unlikely(!map->flags) )
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.5

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