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diff --git a/printbuf.c b/printbuf.c
index e9cde11..b02a363 100644
--- a/printbuf.c
+++ b/printbuf.c
@@ -13,6 +13,7 @@
#include "config.h"
+#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@@ -68,9 +69,16 @@ static int printbuf_extend(struct printbuf *p, int min_size)
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",
@@ -85,6 +93,9 @@ static int printbuf_extend(struct printbuf *p, int min_size)
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;
@@ -136,6 +147,9 @@ int printbuf_memset(struct printbuf *pb, int offset, int charvalue, int len)
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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