Re: [PATCH 4.4 03/26] lib/cmdline.c: fix get_options() overflow while parsing ranges

Ilya Matveychikov
2017-09-27T10:36:26Z

> On Jun 29, 2017, at 7:24 PM, Ben Hutchings <ben.hutchings@codethink.co.uk> wrote:
>
> On Tue, 2017-06-27 at 14:49 +0200, Greg Kroah-Hartman wrote:
>> 4.4-stable review patch. If anyone has any objections, please let me know.
>>
>> ------------------
>>
>> From: Ilya Matveychikov <matvejchikov@gmail.com>
>>
>> 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.
> [...]
>> --- 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)...
>
>> @@ -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.
>
>