[PATCH 2/3] kexec: ensure user memory sizes do not wrap

[Russell King - ARM Linux]

On Thu, Apr 28, 2016 at 07:07:22PM +0800, Minfei Huang wrote:
> On 04/14/16 at 09:00pm, Russell King wrote:
> > Ensure that user memory sizes do not wrap around when validating the
> > user input, which can lead to the following input validation working
> > incorrectly.
> > 
> > Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> > ---
> >  kernel/kexec_core.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> > index 8d34308ea449..d719a4d0ef55 100644
> > --- a/kernel/kexec_core.c
> > +++ b/kernel/kexec_core.c
> > @@ -169,6 +169,8 @@ int sanity_check_segment_list(struct kimage *image)
> >  
> >  		mstart = image->segment[i].mem;
> >  		mend   = mstart + image->segment[i].memsz;
> > +		if (mstart > mend)
> > +			return result;
> 
> The type of image->segment[i].memsz is unsigned. So it is no need to
> have a test here.

Absolutely wrong.  Consider the case:

	segment[i].mem = 0xfff00000;
	segment[i].size = 0x00200000;

Here, mstart will be 0xfff00000, and mend will be 0x00100000.  Just
because it's some random type does not make things magically work.

-- 
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