linux-kernel - Re: [git pull] VFS

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Message-ID: <20110316131502.GS22723@ZenIV.linux.org.uk>
Date:	Wed, 16 Mar 2011 13:15:02 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Theodore Tso <tytso@....EDU>, Dave Chinner <david@...morbit.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [git pull] VFS - the first pile

On Wed, Mar 16, 2011 at 09:07:28AM -0400, Christoph Hellwig wrote:
> On Wed, Mar 16, 2011 at 07:46:40AM -0400, Theodore Tso wrote:
> > 
> > On Mar 16, 2011, at 3:21 AM, Al Viro wrote:
> > 
> > > BTW, you want to update 005 in there - we are back to correct "maximum
> > > is 40 symlinks total, 8 levels on nesting" for all syscalls.  Add the
> > > 41st symlink to your chain in testcase ;-)
> > 
> > Unless there's a way to read out these limits, I'm not sure it's a good idea
> > to add a test like that to xfstests --- it's too fragile since at some point
> > we might change what those limits might be.
> > 
> > Also, xfstests is primarily intended to be a file system level stress tester
> > testing for correctness, and issues of whether we blow up on the 40th, 
> > 41st, or 42nd symlink seems more like an ABI issue --- and even there I'm
> > not sure the ABI specification should be quite that detailed over what's
> > allowed and not allowed.
> 
> That's not what it tests anyway.  It tests that we get ELOOP at some
> point, and do not blow the stack.  Which is someting that older Linux
> code used to do.

Yes.  See patch upthread (or in for-linus).  There are two parts in that
test; *both* would actually trigger the b0rkage in the last commit of
what got merged - the only reason why the first one (long chain) did not
was that the limit got fixed and -ELOOP was no longer triggered.  Symlink
to itself did, of course, trigger it - complete with oops.
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