# Re: \[PATCH v2 5/5\] ucounts: Handle wrapping in is\_ucounts\_overlimit

- From: Shuah Khan \<skhan@linuxfoundation.org\>
- Date: 2022-02-16 17:28:40 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2022/02/1673780
- Thread: https://ratatoskr.run/linux-api/2022/02/1673645/t.md

```text
On 2/16/22 8:58 AM, Eric W. Biederman wrote:
> While examining is_ucounts_overlimit and reading the various messages
> I realized that is_ucounts_overlimit fails to deal with counts that
> may have wrapped.
>
> Being wrapped should be a transitory state for counts and they should
> never be wrapped for long, but it can happen so handle it.
>
> Cc: <redacted>
> Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts")
> Signed-off-by: "Eric W. Biederman" <redacted>
> ---
>   kernel/ucount.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/ucount.c b/kernel/ucount.c
> index 65b597431c86..06ea04d44685 100644
> --- a/kernel/ucount.c
> +++ b/kernel/ucount.c
> @@ -350,7 +350,8 @@ bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsign
>   	if (rlimit > LONG_MAX)
>   		max = LONG_MAX;
>   	for (iter = ucounts; iter; iter = iter->ns->ucounts) {
> -		if (get_ucounts_value(iter, type) > max)
> +		long val = get_ucounts_value(iter, type);
> +		if (val < 0 || val > max)
>   			return true;
>   		max = READ_ONCE(iter->ns->ucount_max[type]);
>   	}
>

This addresses the concerns about overflow.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>

thanks,
-- Shuah
```