Re: [PATCH v4 1/4] mm/mlock: return EINVAL if len overflows for mlock/munlock

[David Hildenbrand]

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@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)));
> > >
> > > 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