From 099016b7e8d70a6d5dd814e788bba08d33d48426 Mon Sep 17 00:00:00 2001 From: Tobias Stoeckmann Date: Mon, 4 May 2020 19:41:16 +0200 Subject: [PATCH 1/3] Protect array_list_del_idx against size_t overflow. If the assignment of stop overflows due to idx and count being larger than SIZE_T_MAX in sum, out of boundary access could happen. It takes invalid usage of this function for this to happen, but I decided to add this check so array_list_del_idx is as safe against bad usage as the other arraylist functions. --- arraylist.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arraylist.c b/arraylist.c index 12ad8af6d3..e5524aca75 100644 --- a/arraylist.c +++ b/arraylist.c @@ -136,6 +136,9 @@ int array_list_del_idx(struct array_list *arr, size_t idx, size_t count) { size_t i, stop; + /* Avoid overflow in calculation with large indices. */ + if (idx > SIZE_T_MAX - count) + return -1; stop = idx + count; if (idx >= arr->length || stop > arr->length) return -1; From 77d935b7ae7871a1940cd827e850e6063044ec45 Mon Sep 17 00:00:00 2001 From: Tobias Stoeckmann Date: Mon, 4 May 2020 19:46:45 +0200 Subject: [PATCH 2/3] 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(+) diff --git a/linkhash.c b/linkhash.c index 7ea58c0abf..f05cc38030 100644 --- a/linkhash.c +++ b/linkhash.c @@ -12,6 +12,7 @@ #include "config.h" +#include #include #include #include @@ -499,6 +500,8 @@ struct lh_table *lh_table_new(int size, lh_entry_free_fn *free_fn, lh_hash_fn *h 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) return NULL; From d07b91014986900a3a75f306d302e13e005e9d67 Mon Sep 17 00:00:00 2001 From: Tobias Stoeckmann Date: Mon, 4 May 2020 19:47:25 +0200 Subject: [PATCH 3/3] 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(-) diff --git a/linkhash.c b/linkhash.c index f05cc38030..51e90b13a2 100644 --- a/linkhash.c +++ b/linkhash.c @@ -580,9 +580,12 @@ int lh_table_insert_w_hash(struct lh_table *t, const void *k, const void *v, con { 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; diff --git a/printbuf.c b/printbuf.c index 976c12dde5..00822fac4f 100644 --- a/printbuf.c +++ b/printbuf.c @@ -15,6 +15,7 @@ #include "config.h" +#include #include #include #include @@ -65,10 +66,16 @@ 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) + /* 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", @@ -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) { + /* 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) @@ -100,6 +110,9 @@ 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) {