From: ebiederm@xmission.com (Eric W. Biederman)
To: Roman Zippel <zippel@fh-brandenburg.de>
Cc: linux-mm@kvack.org
Subject: Re: page locking and error handling
Date: 15 Feb 2001 16:37:59 -0700 [thread overview]
Message-ID: <m1ae7n7c14.fsf@frodo.biederman.org> (raw)
In-Reply-To: Roman Zippel's message of "Thu, 15 Feb 2001 19:50:09 +0100 (MET)"
Roman Zippel <zippel@fh-brandenburg.de> writes:
> Hi,
>
> On 15 Feb 2001, Eric W. Biederman wrote:
>
> > > - if copy_from_user() fails the page is set as not uptodate. AFAIK this
> > > assumes that the page->buffers are still uptodate, so previous writes
> > > are not lost.
> > If copy_from_user fails that invokes undefined behavior, and you just lost
> > your previous writes because you ``overwrote'' them.
>
> What about partial writes?
The important thing is if copy_from_user fails it is because of a buggy
user space app. Because the buggy app passed a bad memory area. So you
have undefined behavior, so you can do whatever is convenient.
The only case to worry about how do we keep from breaking kernel invariants.
I think it make break an invariant to set a mmaped page as not
uptodate, but I can't see any other problems with the interface.
Eric
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next prev parent reply other threads:[~2001-02-15 23:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-15 15:02 page locking and error handling Roman Zippel
2001-02-15 15:33 ` Eric W. Biederman
2001-02-15 18:50 ` Roman Zippel
2001-02-15 23:37 ` Eric W. Biederman [this message]
2001-02-16 18:20 ` Marcelo Tosatti
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