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

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Date:	Sun, 8 Jul 2007 11:12:59 -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, Ulrich Drepper wrote:
> 
> But the real permissions tests are performed in notify_change.  I think
> all this is consistent with how, for instance, fchmod works.  The
> additional tests in fchmod which aren't here (IS_RDONLY and IS_APPEND)
> would also apply to the case where a file name is given.  So, either the
> code was inconsistent already are these tests are really not needed.

No.

notify_change() does *not* do permission checks for 
ATTR_CTIME/MTIME/ATIME.

It does them for the "xxx_SET" attributes, but MTIME/ATIME is expected to 
change when other things change, so notify_change() expects that those 
_other_ changes have been validated from a security standpoint!

utimes() is special.

		Linus
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