zlib: backport fix for heap-based buffer over-read (CVE-2022-37434)

zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow
in inflate in inflate.c via a large gzip header extra field. NOTE: only
applications that call inflateGetHeader are affected. Some common
applications bundle the affected zlib source code but may be unable to
call inflateGetHeader.

Fixes: CVE-2022-37434
References: https://github.com/ivd38/zlib_overflow
Signed-off-by: Petr Štetiar <ynezz@true.cz>

Author: ynezz

package/libs/zlib/patches/006-fix-CVE-2022-37434.patch

@@ -0,0 +1,32 @@
+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.
+---
+ inflate.c | 5 +++--
+ 1 file changed, 3 insertions(+), 2 deletions(-)
+
+diff --git a/inflate.c b/inflate.c
+index 7be8c6366..7a7289749 100644
+--- 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);