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xen/p2m/m2p/gnttab: do not add failed grant maps to m2p override 

The caller will not undo a mapping which failed and therefore the
override will not be removed.

This is especially bad in the case of GNTMAP_contains_pte mapping type
mappings where m2p_add_override will destroy the kernel mapping of the
page.

This was observed via a failure of map_grant_pages in gntdev_mmap (due
to userspace using a bad grant reference), which left the page in
question unmapped (because it was a GNTMAP_contains_pte mapping) which
led to a crash later on.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Ian Campbell 2011-03-04 17:38:21 +00:00 committed by Konrad Rzeszutek Wilk
parent f4ee4af447
commit dc4972a4e2
1 changed files with 4 additions and 0 deletions
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4
drivers/xen/grant-table.c
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@ -462,6 +462,10 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
return ret;
for (i = 0; i < count; i++) {
/* Do not add to override if the map failed. */
if (map_ops[i].status)
continue;
/* m2p override only supported for GNTMAP_contains_pte mappings */
if (!(map_ops[i].flags & GNTMAP_contains_pte))
continue;