[xen stable-4.12] memory: fix off-by-one in XSA-346 change

[patchbot@xxxxxxx]

commit 660254422422f103e797f97545018a1fbc7548e7
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Nov 24 14:14:41 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Nov 24 14:14:41 2020 +0100

    memory: fix off-by-one in XSA-346 change
    
    The comparison against ARRAY_SIZE() needs to be >= in order to avoid
    overrunning the pages[] array.
    
    This is XSA-355.
    
    Fixes: 5777a3742d88 ("IOMMU: hold page ref until after deferred TLB flush")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
    master commit: 9b156bcc3ffcc7949edd4460b718a241e87ae302
    master date: 2020-11-24 14:01:31 +0100
---
 xen/common/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index b352a30af6..8aea327df4 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -861,7 +861,7 @@ int xenmem_add_to_physmap(struct domain *d, struct 
xen_add_to_physmap *xatp,
             ++extra.ppage;
 
         /* Check for continuation if it's not the last iteration. */
-        if ( (++done > ARRAY_SIZE(pages) && extra.ppage) ||
+        if ( (++done >= ARRAY_SIZE(pages) && extra.ppage) ||
              (xatp->size > done && hypercall_preempt_check()) )
         {
             rc = start + done;
--
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