linux-kernel - Re: [PATCH] dcache: fix locking bug in __dentry

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Message-ID: <20140124122409.GT10323@ZenIV.linux.org.uk>
Date:	Fri, 24 Jan 2014 12:24:09 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dcache: fix locking bug in __dentry_path()

On Fri, Jan 24, 2014 at 11:21:26AM +0100, Denys Vlasenko wrote:
> If given buffer size is zero, we forget to rcu_read_unlock()
> on error path.

Er...  Where could we ever get called with size zero?  IOW, the
real question is whether that check makes any sense.  If nothing
else, a much more obvious fix (again, assuming there is a call
chain that could have triggered that in the first place), would
be to take that
        if (buflen < 1)
                goto Elong;
on the very top of __dentry_path().  Note that buflen never
change, so this check could bloody well be handled once - and
earlier.  But again, the callers shouldn't be calling it that
way...
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