thodg/libgit2

2018-08-09T12:48:26

diff: fix OOM on AIX when finding similar deltas in empty diff The function `git_diff_find_similar` keeps a function of cache similarity metrics signatures, whose size depends on the number of deltas passed in via the `diff` parameter. In case where the diff is empty and thus doesn't have any deltas at all, we may end up allocating this cache via a call to `git__calloc(0, sizeof(void *))`. At least on AIX, allocating 0 bytes will result in a `NULL` pointer being returned, which causes us to erroneously return an OOM error. Fix this situation by simply returning early in case where we are being passed an empty diff, as we cannot find any similarities in that case anyway.

diff --git a/src/diff_tform.c b/src/diff_tform.c
index 7133065..42da150 100644
--- a/src/diff_tform.c
+++ b/src/diff_tform.c
@@ -822,7 +822,7 @@ int git_diff_find_similar(
 	num_deltas = diff->deltas.length;
 
 	/* TODO: maybe abort if deltas.length > rename_limit ??? */
-	if (!git__is_uint32(num_deltas))
+	if (!num_deltas || !git__is_uint32(num_deltas))
 		goto cleanup;
 
 	/* No flags set; nothing to do */