On Jun 29, 2017, at 7:24 PM, Ben Hutchings [off-list ref] wrote:

On Tue, 2017-06-27 at 14:49 +0200, Greg Kroah-Hartman wrote:

quoted

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ilya Matveychikov <redacted>

commit a91e0f680bcd9e10c253ae8b62462a38bd48f09f upstream.

When using get_options() it's possible to specify a range of numbers,
like 1-100500.  The problem is that it doesn't track array size while
calling internally to get_range() which iterates over the range and
fills the memory with numbers.

[...]

quoted

--- a/lib/cmdline.c
+++ b/lib/cmdline.c

@@ -22,14 +22,14 @@
 *	the values[M, M+1, ..., N] into the ints array in get_options.
 */

-static int get_range(char **str, int *pint)
+static int get_range(char **str, int *pint, int n)

{
	int x, inc_counter, upper_range;

	(*str)++;
	upper_range = simple_strtol((*str), NULL, 0);
	inc_counter = upper_range - *pint;
-	for (x = *pint; x < upper_range; x++)
+	for (x = *pint; n && x < upper_range; x++, n--)
		*pint++ = x;
	return inc_counter;
}

But this still returns the number of integers in the range (minus 1)...

quoted

@@ -96,7 +96,7 @@ char *get_options(const char *str, int n

			break;
		if (res == 3) {
			int range_nums;
-			range_nums = get_range((char **)&str, ints + i);
+			range_nums = get_range((char **)&str, ints + i, nints - i);
			if (range_nums < 0)
				break;
			/*

...so that get_options() may set i > nints and ints[0] > nints - 1.
That will presumably result in out-of-bounds reads in callers.

(This set of functions really deserves to be given a test suite and then
rewritten, because they are a *mess*.)

Please review the approach of fixing that:
https://lkml.org/lkml/2017/9/19/105

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.