[PULL v1 3/3] xen: mapcache: Fix unmapping of first entries in buckets

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

From: "Edgar E. Iglesias" <edgar.iglesias@amd.com>

This fixes the clobbering of the entry->next pointer when
unmapping the first entry in a bucket of a mapcache.

Fixes: 123acd816d ("xen: mapcache: Unmap first entries in buckets")
Reported-by: Anthony PERARD <anthony.perard@vates.tech>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Anthony PERARD <anthony.perard@vates.tech>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
---
 hw/xen/xen-mapcache.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
index 5f23b0adbe..18ba7b1d8f 100644
--- a/hw/xen/xen-mapcache.c
+++ b/hw/xen/xen-mapcache.c
@@ -597,7 +597,17 @@ static void xen_invalidate_map_cache_entry_unlocked(MapCache *mc,
         pentry->next = entry->next;
         g_free(entry);
     } else {
-        memset(entry, 0, sizeof *entry);
+        /*
+         * Invalidate mapping but keep entry->next pointing to the rest
+         * of the list.
+         *
+         * Note that lock is already zero here, otherwise we don't unmap.
+         */
+        entry->paddr_index = 0;
+        entry->vaddr_base = NULL;
+        entry->valid_mapping = NULL;
+        entry->flags = 0;
+        entry->size = 0;
     }
 }
 
-- 
2.43.0