Fix extra field processing bug that dereferences NULL state->head.

The recent commit to fix a gzip header extra field processing bug introduced the new bug fixed here.
madler · Aug 8, 2022 · 1eb7682 · 1eb7682
1 parent 22aec0c
commit 1eb7682
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/inflate.c b/inflate.c
@@ -763,10 +763,10 @@ int flush;
                 copy = state->length;
                 if (copy > have) copy = have;
                 if (copy) {
-                    len = state->head->extra_len - state->length;
                     if (state->head != Z_NULL &&
                         state->head->extra != Z_NULL &&
-                        len < state->head->extra_max) {
+                        (len = state->head->extra_len - state->length) <
+                            state->head->extra_max) {
                         zmemcpy(state->head->extra + len, next,
                                 len + copy > state->head->extra_max ?
                                 state->head->extra_max - len : copy);