Re: [PATCH 0/4] return EINVAL for illegal user memory range

David Hildenbrand
2023-01-02T13:23:20Z

On 05.12.22 04:41, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@huawei.com>
>
> While testing mlock, we have a problem if the len of mlock is ULONG_MAX.
> The return value of mlock is zero. But nothing will be locked since the
> len in do_mlock overflows to zero due to the following code in mlock:
>
> len = PAGE_ALIGN(len + (offset_in_page(start)));
>
> However this problem appear in multiple syscalls.
>
> Since TASK_SIZE is the maximum user space address. The start or len of
> mlock shouldn't be bigger than this. Function access_ok can be used to
> check this issue, so return -EINVAL if bigger.

I assume this makes sure that what we document holds:

EINVAL (mlock(), mlock2(), and munlock()) The result of the addition
addr+len was less than addr (e.g., the addition may have
resulted in an overflow).

So instead of adding access_ok() checks, wouldn't be the right think to
do checking for overflows?

--
Thanks,

David / dhildenb