From 1eb7682f845ac9e9bf9ae35bbfb3bad5dacbd91d Mon Sep 17 00:00:00 2001

From: Mark Adler <fork@madler.net>

Date: Mon, 8 Aug 2022 10:50:09 -0700

Subject: [PATCH] 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.

---

 inflate.c | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/inflate.c b/inflate.c

index 7a72897..2a3c4fe 100644

--- 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);

-- 

2.35.3