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Fix integer overflows.

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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.
This commit is contained in:
Tobias Stoeckmann
2020-05-04 19:47:25 +02:00
parent 77d935b7ae
commit d07b910149
2 changed files with 21 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
linkhash.c
View File

@@ -580,9 +580,12 @@ int lh_table_insert_w_hash(struct lh_table *t, const void *k, const void *v, con
{ {
unsigned long n; unsigned long n;
if (t->count >= t->size * LH_LOAD_FACTOR) if (t->count >= t->size * LH_LOAD_FACTOR) {
if (lh_table_resize(t, t->size * 2) != 0) /* 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; return -1;
}
n = h % t->size; n = h % t->size;

19
printbuf.c
View File

@@ -15,6 +15,7 @@
#include "config.h" #include "config.h"
#include <limits.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
#include <string.h> #include <string.h>
@@ -65,10 +66,16 @@ static int printbuf_extend(struct printbuf *p, int min_size)
if (p->size >= min_size) if (p->size >= min_size)
return 0; return 0;
/* Prevent signed integer overflows with large buffers. */
new_size = p->size * 2; if (min_size > INT_MAX - 8)
if (new_size < min_size + 8) return -1;
if (p->size > INT_MAX / 2)
new_size = min_size + 8; 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 #ifdef PRINTBUF_DEBUG
MC_DEBUG("printbuf_memappend: realloc " MC_DEBUG("printbuf_memappend: realloc "
"bpos=%d min_size=%d old_size=%d new_size=%d\n", "bpos=%d min_size=%d old_size=%d new_size=%d\n",
@@ -83,6 +90,9 @@ static int printbuf_extend(struct printbuf *p, int min_size)
int printbuf_memappend(struct printbuf *p, const char *buf, int 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 (p->size <= p->bpos + size + 1)
{ {
if (printbuf_extend(p, p->bpos + size + 1) < 0) if (printbuf_extend(p, p->bpos + size + 1) < 0)
@@ -100,6 +110,9 @@ int printbuf_memset(struct printbuf *pb, int offset, int charvalue, int len)
if (offset == -1) if (offset == -1)
offset = pb->bpos; offset = pb->bpos;
/* Prevent signed integer overflows with large buffers. */
if (len > INT_MAX - offset)
return -1;
size_needed = offset + len; size_needed = offset + len;
if (pb->size < size_needed) if (pb->size < size_needed)
{ {