Vendor import of xz 5.4.2 (trimmed)vendor/xz/5.4.2

1 files changed, 14 insertions, 6 deletions

diff --git a/src/liblzma/common/common.c b/src/liblzma/common/common.c
index a708fdf187a6..baad3dd84c7b 100644
--- a/src/liblzma/common/common.c
+++ b/src/liblzma/common/common.c
@@ -288,13 +288,21 @@ lzma_code(lzma_stream *strm, lzma_action action)
 			strm->next_in, &in_pos, strm->avail_in,
 			strm->next_out, &out_pos, strm->avail_out, action);
 
-	strm->next_in += in_pos;
-	strm->avail_in -= in_pos;
-	strm->total_in += in_pos;
+	// Updating next_in and next_out has to be skipped when they are NULL
+	// to avoid null pointer + 0 (undefined behavior). Do this by checking
+	// in_pos > 0 and out_pos > 0 because this way NULL + non-zero (a bug)
+	// will get caught one way or other.
+	if (in_pos > 0) {
+		strm->next_in += in_pos;
+		strm->avail_in -= in_pos;
+		strm->total_in += in_pos;
+	}
 
-	strm->next_out += out_pos;
-	strm->avail_out -= out_pos;
-	strm->total_out += out_pos;
+	if (out_pos > 0) {
+		strm->next_out += out_pos;
+		strm->avail_out -= out_pos;
+		strm->total_out += out_pos;
+	}
 
 	strm->internal->avail_in = strm->avail_in;