linux-kernel - Re: BUG_ON(nd->inode != parent->d

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Message-ID: <20130309025752.GA13913@redhat.com>
Date:	Fri, 8 Mar 2013 21:57:52 -0500
From:	Dave Jones <davej@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Cc:	ebiederm@...ssion.com
Subject: Re: BUG_ON(nd->inode != parent->d_inode);

On Fri, Mar 08, 2013 at 09:56:31PM -0500, Dave Jones wrote:
 > On Fri, Mar 08, 2013 at 09:26:23PM -0500, Dave Jones wrote:
 >  > On Fri, Mar 08, 2013 at 06:08:52PM -0800, Linus Torvalds wrote:
 >  >  > On Fri, Mar 8, 2013 at 6:03 PM, Dave Jones <davej@...hat.com> wrote:
 >  >  > >
 >  >  > > existing pathname + 'a' = fine.
 >  >  > >
 >  >  > > existing pathname + '/' + 'a' = boom.
 >  >  > 
 >  >  > Good.
 >  >  > 
 >  >  > > Looks like if I do this..
 >  >  > >
 >  >  > >        if (isdigit(newpath[len]) != 0) {
 >  >  > >                 newpath[len] = '/';
 >  >  > >                newpath[len+1] = 'A';
 >  >  > >                newpath[len+2] = 0;
 >  >  > >
 >  >  > > no bug.
 >  >  > 
 >  >  > Well, but that will never trigger. newpath[len] will always be NUL, so
 >  >  > you just disabled things entirely. Use "len-1".
 >  >  > 
 >  >  > So I don't think that did what you meant it to do.
 >  > 
 >  > Fixed that up, and even double checked my sanity by printing stuff out.
 >  > 
 >  > Confirmed that it's something that doesn't end in a number.
 >  
 > I've got a hunch that it's /proc/$$/ns/uts.
 > 
 > After 3-4 runs, that's the only common file in the last few that got mangled.
 > 
 > I'll do some more tests, but this might be the one.
 
confirmed.  A simple 

mkdir /proc/self/ns/uts/A

will trigger it.

Eric ?

	Dave

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