linux-kernel - Re: [PATCH] dcache: Translating dentry into pathname without taking rename

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Message-ID: <20130904194341.GL13318@ZenIV.linux.org.uk>
Date:	Wed, 4 Sep 2013 20:43:41 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Waiman Long <waiman.long@...com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH] dcache: Translating dentry into pathname without taking
 rename_lock

On Wed, Sep 04, 2013 at 03:33:00PM -0400, Waiman Long wrote:

> I have thought about that. But if a d_move() is going on, the string
> in the buffer will be discarded as the sequence number will change.
> So whether or not it have embedded null byte shouldn't matter. That
> is why I didn't add code to do byte-by-byte copy at this first
> patch. I can add code to do that if you think it is safer to do so.

Sigh...  Junk in the output is not an issue; reading from invalid address
is, since you might not survive to the sequence number check.  Again,
if p is an address returned by kmalloc(size, ...), dereferencing p + offset
is not safe unless offset is less than size.
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