Re: [PATCH] dcache: Translating dentry into pathname without takingrename_lock

From: Al Viro
Date: Wed Sep 04 2013 - 15:43:48 EST


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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