fedora 25
integer weakness #30

2

Weakness Breakdown


Definition:

An integer overflow occurs when the answer to an arithmetic operation exceeds the maximum size of the integer type used to store it. The resulting value will appear to have wrapped around the maximum value and started again at the minimum value. This would look like a clock that represents 13:00 by pointing at 1:00. An attacker can use an integer overflow during a buffer length calculation, which results in the allocated buffer being too small to hold the data copied into it, thus causing a buffer overflow.

Warning code(s):

Unless checked, the resulting number can exceed the expected range.

File Name:

blktrace-1.1.0/blktrace.c

Context:

The highlighted line of code below is the trigger point of this particular Fedora 25 integer weakness.

 }

static int get_drops(struct devpath *dpp)
{
	int fd, drops = 0;
	char fn[MAXPATHLEN + 64], tmp[256];

	snprintf(fn, sizeof(fn), "%s/block/%s/dropped", debugfs_path,
		 dpp->buts_name);

	fd = my_open(fn, O_RDONLY);
	if (fd < 0) {
		/*
		 * This may be ok: the kernel may not support
		 * dropped counts.
		 */
		if (errno != ENOENT)
			fprintf(stderr, "Could not open %s: %d/%s\n",
				fn, errno, strerror(errno));
		return 0;
	} else if (read(fd, tmp, sizeof(tmp)) < 0) {
		fprintf(stderr, "Could not read %s: %d/%s\n",
			fn, errno, strerror(errno));
	} else
		drops = atoi(tmp);
	close(fd);

	return drops;
}

static void get_all_drops(void)
{
	struct list_head *p;

	__list_for_each(p, &devpaths) {
		struct devpath *dpp = list_entry(p, struct devpath, head);

		dpp->drops = get_drops(dpp);
	}
}

static inline struct trace_buf *alloc_trace_buf(int cpu, int bufsize)
{
	struct trace_buf *tbp;

	tbp = malloc(sizeof(*tbp) + bufsize);
	INIT_LIST_HEAD(&tbp->head);
	tbp->len = 0;
	tbp->buf = (void *)(tbp + 1);
	tbp->cpu = cpu; 

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