libsparse: use strcmp and validate last_used pointer
This patch is used to fix two Bugs in backed_block.c
First, fix wrong comparing string way: we should use strcmp rather than
just compare their address. Second, fix using illegal memory risk in
bbl->last_used pointer. When entering queue_bb function,
bbl->last_used = new_bb, but in the following code if
queue_bb(xx, bb, new_bb) return ok, the space of new_bb is released. So
next time, if you use bbl->last_used pointer, may cause segment fault !
Change-Id: I6abb505f9b903b697448639fc64fb7518df5cca1
diff --git a/libsparse/backed_block.c b/libsparse/backed_block.c
index 3e72b57..794cd6b 100644
--- a/libsparse/backed_block.c
+++ b/libsparse/backed_block.c
@@ -221,7 +221,8 @@
}
break;
case BACKED_BLOCK_FILE:
- if (a->file.filename != b->file.filename ||
+ /* Already make sure b->type is BACKED_BLOCK_FILE */
+ if (strcmp(a->file.filename, b->file.filename) ||
a->file.offset + a->len != b->file.offset) {
return -EINVAL;
}
@@ -279,7 +280,10 @@
}
merge_bb(bbl, new_bb, new_bb->next);
- merge_bb(bbl, bb, new_bb);
+ if (!merge_bb(bbl, bb, new_bb)) {
+ /* new_bb destroyed, point to retained as last_used */
+ bbl->last_used = bb;
+ }
return 0;
}