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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
- @@ -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)
- {
|
