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

From: David Hildenbrand
Date: Mon Jan 02 2023 - 08:23:20 EST


On 05.12.22 04:41, Wupeng Ma wrote:
From: Ma Wupeng <mawupeng1@xxxxxxxxxx>

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