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

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Date:	Thu, 3 May 2007 06:55:36 -0400
From:	Robin Getz <rgetz@...ckfin.uclinux.org>
To:	"Greg Ungerer" <gerg@...pgear.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH]: linux-2.6.21-uc0 (MMU-less updates)

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?

-Robin
-
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