linux-kernel - Re: 2.6.22-rc6(mm1) Unable to handle kernel NULL pointer dereference

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Message-ID: <alpine.LFD.0.999.0707081130420.31544@woody.linux-foundation.org>
Date:	Sun, 8 Jul 2007 11:38:20 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ulrich Drepper <drepper@...hat.com>
cc:	Al Viro <viro@....linux.org.uk>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.22-rc6(mm1) Unable to handle kernel NULL pointer dereference
 - git-bisect result

On Sun, 8 Jul 2007, Linus Torvalds wrote:
> 
> This would seem to be the minimal change, and I think it's right.

Side note: I considered just changing do_utimes() to use 
ATIME_SET/MTIME_SET instead, which would simplify the logic a lot..

But it turns out that the semantics for A/MTIME_SET is that only the owner 
of the file can do that. So the "!times" case is simply _fundamentally_ 
different from a permissions check standpoint, and there we have to check 
for "writable" rather than anything else (although ownership will override 
it).

So rather than simplify the thing, I had to add code. Oh, well.

I do think that it would be even nicer to just have a function that fills 
in the "struct nameidata" from the dfd. I think we should be able to: the 
"struct file" really does have the "f_path" thing with both dentry and mnt 
information, and that would clean up that whole ugly "filepointer-vs-nd" 
thing a lot.

That would be an "Al cleanup", though. What do you think, Al?

			Linus
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