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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
@@ -579,9 +579,12 @@ int lh_table_insert_w_hash(struct lh_tab
{
unsigned long n;
- if (t->count >= t->size * LH_LOAD_FACTOR)
- if (lh_table_resize(t, t->size * 2) != 0)
+ if (t->count >= t->size * LH_LOAD_FACTOR) {
+ /* Avoid signed integer overflow with large tables. */
+ int new_size = INT_MAX / 2 < t->size ? t->size * 2 : INT_MAX;
+ if (t->size == INT_MAX || lh_table_resize(t, new_size) != 0)
return -1;
+ }
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>
@@ -65,9 +66,16 @@ static int printbuf_extend(struct printb
if (p->size >= min_size)
return 0;
- new_size = p->size * 2;
- if (new_size < min_size + 8)
- new_size = 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",
@@ -82,6 +90,9 @@ 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;
@@ -98,6 +109,9 @@ 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)
{
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