Re: [PATCH]: linux-2.6.21-uc0 (MMU-less updates)

[Greg Ungerer <gerg@snapgear.com>]

Robin Getz wrote:
> On Wed 2 May 2007 07:32, Greg Ungerer pondered:
> > Robin Getz wrote:
> > > On Wed 2 May 2007 01:23, Greg Ungerer pondered:
> > > > diff -Naur linux-2.6.21/fs/namei.c linux-2.6.21-uc0/fs/namei.c
> > > > --- linux-2.6.21/fs/namei.c     2007-05-01 17:12:53.000000000 +1000
> > > > +++ linux-2.6.21-uc0/fs/namei.c 2007-05-01 17:16:18.000000000 +1000
> > > > @@ -120,12 +120,14 @@
> > > >         int retval;
> > > >         unsigned long len = PATH_MAX;
> > > >
> > > > +#ifdef CONFIG_MMU
> > > >         if (!segment_eq(get_fs(), KERNEL_DS)) {
> > > >                 if ((unsigned long) filename >= TASK_SIZE)
> > > >                         return -EFAULT;
> > > >                 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
> > > >                         len = TASK_SIZE - (unsigned long) filename;
> > > >         }
> > > > +#endif
> > > >
> > > >         retval = strncpy_from_user(page, filename, len);
> > > >         if (retval > 0) {
> > > I was trying to understand why we don't want to do the same checking on
> > > noMMU?
> > The problem is on systems that have RAM mapped at high physical
> > addresses. TASK_SIZE may well be a numerically smaller number
> > than the address range that RAM sits in. So this test fails when
> > it shouldn't.
>
> So, then this is a problem only on one or two architectures, not all noMMU 
> platforms?

Its not an architecture problem. It can effect any board that
has RAM mapped at a large numerical addresses (larger than TASK_SIZE).
So it can effect any non-MMU platform.

Regards
Greg



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Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg@snapgear.com
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