xen/blkback: potential null dereference in error handling

blkbk->pending_pages can be NULL here so I added a check for it.

Signed-off-by: Dan Carpenter <error27@gmail.com>
[v1: Redid the loop a bit]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index c73910cc28c9..5cf2993a8338 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -809,11 +809,13 @@ static int __init xen_blkif_init(void)
  failed_init:
         kfree(blkbk->pending_reqs);
         kfree(blkbk->pending_grant_handles);
-        for (i = 0; i < mmap_pages; i++) {
-                if (blkbk->pending_pages[i])
-                        __free_page(blkbk->pending_pages[i]);
+        if (blkbk->pending_pages) {
+                for (i = 0; i < mmap_pages; i++) {
+                        if (blkbk->pending_pages[i])
+                                __free_page(blkbk->pending_pages[i]);
+                }
+                kfree(blkbk->pending_pages);
         }
-        kfree(blkbk->pending_pages);
         kfree(blkbk);
         blkbk = NULL;
         return rc;