https://bugs.gentoo.org/863851
https://github.com/madler/zlib/commit/eff308af425b67093bab25f80f1ae950166bece1
https://github.com/madler/zlib/commit/1eb7682f845ac9e9bf9ae35bbfb3bad5dacbd91d (see https://github.com/curl/curl/issues/9271)

From eff308af425b67093bab25f80f1ae950166bece1 Mon Sep 17 00:00:00 2001
From: Mark Adler <fork@madler.net>
Date: Sat, 30 Jul 2022 15:51:11 -0700
Subject: [PATCH] Fix a bug when getting a gzip header extra field with
 inflate().

If the extra field was larger than the space the user provided with
inflateGetHeader(), and if multiple calls of inflate() delivered
the extra header data, then there could be a buffer overflow of the
provided space. This commit assures that provided space is not
exceeded.
--- a/inflate.c
+++ b/inflate.c
@@ -763,9 +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_len - state->length;
+                        state->head->extra != Z_NULL &&
+                        len < state->head->extra_max) {
                         zmemcpy(state->head->extra + len, next,
                                 len + copy > state->head->extra_max ?
                                 state->head->extra_max - len : copy);

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.
--- 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);