libjson-c: backport security fixes

This backports upstream fixes for the out of bounds write vulnerability in json-c.
It was reported and patches in this upstream PR: https://github.com/json-c/json-c/pull/592

Addresses CVE-2020-12762

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Signed-off-by: Luka Perkov <luka.perkov@sartura.hr>
[bump PKG_RELEASE, rebase patches on top of json-c 0.12]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
(backported from commit bc0288b768)

package/libs/libjson-c/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=json-c
 PKG_VERSION:=0.12.1
-PKG_RELEASE:=3
+PKG_RELEASE:=3.1
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION)-nodoc.tar.gz
 PKG_SOURCE_URL:=https://s3.amazonaws.com/json-c_releases/releases/

package/libs/libjson-c/patches/000-libm.patch

@@ -1,6 +1,6 @@
 --- a/configure.ac
 +++ b/configure.ac
-@@ -43,12 +43,6 @@
+@@ -43,12 +43,6 @@ AC_FUNC_MEMCMP
  AC_FUNC_MALLOC
  AC_FUNC_REALLOC
  AC_CHECK_FUNCS(strcasecmp strdup strerror snprintf vsnprintf vasprintf open vsyslog strncasecmp setlocale)

package/libs/libjson-c/patches/001-Prevent-division-by-zero-in-linkhash.patch

@@ -0,0 +1,32 @@
+From 77d935b7ae7871a1940cd827e850e6063044ec45 Mon Sep 17 00:00:00 2001
+From: Tobias Stoeckmann <tobias@stoeckmann.org>
+Date: Mon, 4 May 2020 19:46:45 +0200
+Subject: [PATCH 2/2] Prevent division by zero in linkhash.
+
+If a linkhash with a size of zero is created, then modulo operations
+are prone to division by zero operations.
+
+Purely protective measure against bad usage.
+---
+ linkhash.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+--- a/linkhash.c
++++ b/linkhash.c
+@@ -10,6 +10,7 @@
+  *
+  */
+ 
++#include <assert.h>
+ #include <stdio.h>
+ #include <string.h>
+ #include <stdlib.h>
+@@ -431,6 +432,8 @@ struct lh_table* lh_table_new(int size,
+ 	int i;
+ 	struct lh_table *t;
+ 
++  /* Allocate space for elements to avoid divisions by zero. */
++  assert(size > 0);
+ 	t = (struct lh_table*)calloc(1, sizeof(struct lh_table));
+ 	if(!t) lh_abort("lh_table_new: calloc failed\n");
+ 	t->count = 0;

package/libs/libjson-c/patches/002-Fix-integer-overflows.patch

@@ -0,0 +1,83 @@
+From d07b91014986900a3a75f306d302e13e005e9d67 Mon Sep 17 00:00:00 2001
+From: Tobias Stoeckmann <tobias@stoeckmann.org>
+Date: Mon, 4 May 2020 19:47:25 +0200
+Subject: [PATCH] Fix integer overflows.
+
+The data structures linkhash and printbuf are limited to 2 GB in size
+due to a signed integer being used to track their current size.
+
+If too much data is added, then size variable can overflow, which is
+an undefined behaviour in C programming language.
+
+Assuming that a signed int overflow just leads to a negative value,
+like it happens on many sytems (Linux i686/amd64 with gcc), then
+printbuf is vulnerable to an out of boundary write on 64 bit systems.
+---
+ linkhash.c |  7 +++++--
+ printbuf.c | 19 ++++++++++++++++---
+ 2 files changed, 21 insertions(+), 5 deletions(-)
+
+--- a/linkhash.c
++++ b/linkhash.c
+@@ -498,7 +498,12 @@ int lh_table_insert(struct lh_table *t,
+ 	unsigned long h, n;
+ 
+ 	t->inserts++;
+-	if(t->count >= t->size * LH_LOAD_FACTOR) lh_table_resize(t, t->size * 2);
++	if(t->count >= t->size * LH_LOAD_FACTOR) {
++		/* Avoid signed integer overflow with large tables. */
++		int new_size = (t->size > INT_MAX / 2) ? INT_MAX : (t->size * 2);
++		if (t->size != INT_MAX)
++			lh_table_resize(t, new_size);
++	}
+ 
+ 	h = t->hash_fn(k);
+ 	n = h % t->size;
+--- a/printbuf.c
++++ b/printbuf.c
+@@ -15,6 +15,7 @@
+ 
+ #include "config.h"
+ 
++#include <limits.h>
+ #include <stdio.h>
+ #include <stdlib.h>
+ #include <string.h>
+@@ -63,7 +64,16 @@ static int printbuf_extend(struct printb
+ 	if (p->size >= min_size)
+ 		return 0;
+ 
+-	new_size = json_max(p->size * 2, min_size + 8);
++	/* Prevent signed integer overflows with large buffers. */
++	if (min_size > INT_MAX - 8)
++		return -1;
++	if (p->size > INT_MAX / 2)
++		new_size = min_size + 8;
++	else {
++		new_size = p->size * 2;
++		if (new_size < min_size + 8)
++			new_size = min_size + 8;
++	}
+ #ifdef PRINTBUF_DEBUG
+ 	MC_DEBUG("printbuf_memappend: realloc "
+ 	  "bpos=%d min_size=%d old_size=%d new_size=%d\n",
+@@ -78,6 +88,9 @@ static int printbuf_extend(struct printb
+ 
+ int printbuf_memappend(struct printbuf *p, const char *buf, int size)
+ {
++  /* Prevent signed integer overflows with large buffers. */
++  if (size > INT_MAX - p->bpos - 1)
++    return -1;
+   if (p->size <= p->bpos + size + 1) {
+     if (printbuf_extend(p, p->bpos + size + 1) < 0)
+       return -1;
+@@ -94,6 +107,9 @@ int printbuf_memset(struct printbuf *pb,
+ 
+ 	if (offset == -1)
+ 		offset = pb->bpos;
++	/* Prevent signed integer overflows with large buffers. */
++	if (len > INT_MAX - offset)
++		return -1;
+ 	size_needed = offset + len;
+ 	if (pb->size < size_needed)
+ 	{