On Tue, Jul 30, 2019 at 10:05:42AM -0400, Boris Ostrovsky wrote: > On 7/30/19 2:03 AM, Souptick Joarder wrote: > > On Mon, Jul 29, 2019 at 7:06 PM Marek Marczykowski-Górecki > > <marmarek@xxxxxxxxxxxxxxxxxxxxxx> wrote: > >> On Mon, Jul 29, 2019 at 02:02:54PM +0530, Souptick Joarder wrote: > >>> On Mon, Jul 29, 2019 at 1:35 PM Souptick Joarder <jrdr.linux@xxxxxxxxx> wrote: > >>>> On Sun, Jul 28, 2019 at 11:36 PM Marek Marczykowski-Górecki > >>>> <marmarek@xxxxxxxxxxxxxxxxxxxxxx> wrote: > >>>>> On Fri, Feb 15, 2019 at 08:18:31AM +0530, Souptick Joarder wrote: > >>>>>> Convert to use vm_map_pages() to map range of kernel > >>>>>> memory to user vma. > >>>>>> > >>>>>> map->count is passed to vm_map_pages() and internal API > >>>>>> verify map->count against count ( count = vma_pages(vma)) > >>>>>> for page array boundary overrun condition. > >>>>> This commit breaks gntdev driver. If vma->vm_pgoff > 0, vm_map_pages > >>>>> will: > >>>>> - use map->pages starting at vma->vm_pgoff instead of 0 > >>>> The actual code ignores vma->vm_pgoff > 0 scenario and mapped > >>>> the entire map->pages[i]. Why the entire map->pages[i] needs to be mapped > >>>> if vma->vm_pgoff > 0 (in original code) ? > >> vma->vm_pgoff is used as index passed to gntdev_find_map_index. It's > >> basically (ab)using this parameter for "which grant reference to map". > >> > >>>> are you referring to set vma->vm_pgoff = 0 irrespective of value passed > >>>> from user space ? If yes, using vm_map_pages_zero() is an alternate > >>>> option. > >> Yes, that should work. > > I prefer to use vm_map_pages_zero() to resolve both the issues. Alternatively > > the patch can be reverted as you suggested. Let me know you opinion and wait > > for feedback from others. > > > > Boris, would you like to give any feedback ? > > vm_map_pages_zero() looks good to me. Marek, does it work for you? Yes, replacing vm_map_pages() with vm_map_pages_zero() fixes the problem for me. -- Best Regards, Marek Marczykowski-Górecki Invisible Things Lab A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing?
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