Re: [PATCH] mm: fix incorrect behavior when process virtual address space limit is exceeded

[Chris Metcalf]

On 11/17/2015 11:19 AM, Oleg Nesterov wrote:
> On 11/16, Piotr Kwapulinski wrote:
> > @@ -1551,7 +1552,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> >   		 * MAP_FIXED may remove pages of mappings that intersects with
> >   		 * requested mapping. Account for the pages it would unmap.
> >   		 */
> > -		if (!(vm_flags & MAP_FIXED))
> > +		if (!(flags & MAP_FIXED))
> >   			return -ENOMEM;
> And afaics arch/tile/mm/elf.c can use do_mmap(MAP_FIXED ...) rather than
> mmap_region(), it can be changed by a separate patch. In this case we can
> unexport mmap_region().

The problem is that we are mapping a region of virtual address space that
the chip provides for setting up interrupt handlers (at 0xfc000000) but that
is above the TASK_SIZE cutoff, so do_mmap() would fail the call in
get_unmapped_area().

--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com

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