Messages in this thread | | | Date | Wed, 28 Dec 2022 14:17:01 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 1/4] mm/mlock: return EINVAL for illegal user memory range in mlock |
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On Mon, 5 Dec 2022 11:41:05 +0800 Wupeng Ma <mawupeng1@huawei.com> wrote:
> 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))); > > The same problem happens in munlock. > > 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.
What happens if userspace uses a value somewhat smaller than ULONG_MAX?
mlock(addr, ULONG_MAX - 1000000);
?
Because if the above works successfully and if it no longer works successfully with this patchset then that could be a backward-compatibility problem.
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