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Date: Sun, 29 Oct 2000 15:42:37 -0500 (EST)
From: Alexander Viro <viro@math.psu.edu>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
cc: Linus Torvalds <torvalds@transmeta.com>,
        Paul Mackerras <paulus@linuxcare.com.au>, linux-kernel@vger.kernel.org
Subject: Re: page->mapping == 0
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On Sun, 29 Oct 2000, Alan Cox wrote:

> > I would expect problems with truncate, mmap, rename, POSIX locks, fasync,
> > ptrace and mount go unnoticed for _long_. Ditto for parts of procfs
> 
> Well the ptrace one still has mysteriously breaks usermode linux against it
> on my list here. Was that ever explained. It looked like the stack got corrupted
> which is weird.

Alan, is it me or usermode port really tends to catch the stack overflows?
<thinks> How about we allocate the pages by 4, not by 2 as we do now, and
explicitly unmap the pages below the task_struct? That would still leave the
chance of stack overflow going unnoticed, but the window would be limited.

Another possibility for ptrace-related screwups: past-the-EOF check in
filemap_nopage(). I'm still not convinced that it's right. It may be, but...

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