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SubjectRe: [PATCH v4 1/4] mm/mlock: return EINVAL if len overflows for mlock/munlock
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On 21.03.23 08:44, mawupeng wrote:
>
>
> On 2023/3/20 18:54, David Hildenbrand wrote:
>> On 20.03.23 03:47, 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)));
>>>
>>> The same problem happens in munlock.
>>>
>>> Add new check and return -EINVAL to fix this overflowing scenarios since
>>> they are absolutely wrong.
>>
>> Thinking again, wouldn't we reject mlock(0, ULONG_MAX) now as well?
>
> mlock will return 0 if len is zero which is the same w/o this patchset.
> Here is the calltrace if len is zero.
>
> mlock(len == 0)
> do_mlock(len == 0)
> if (!len)
> return 0
>

I was asking about addr=0, len=ULONG_MAX.

IIUC, that used to work but could now fail? I haven't played with it,
though.

--
Thanks,

David / dhildenb

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