Date: Sat, 25 Aug 2012 20:12:18 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Pavel Emelyanov <xemul@parallels.com>,
        James Bottomley <jbottomley@parallels.com>,
        Matthew Helsley <matt.helsley@gmail.com>,
        aneesh.kumar@linux.vnet.ibm.com, bfields@fieldses.org
Subject: Re: [patch 1/9] procfs: Move /proc/pid/fd[info] handling code to
 fd.[ch]
Message-ID: <20120825191218.GV23464@ZenIV.linux.org.uk>
References: <20120823104323.040550004@openvz.org>
 <20120823104725.592602491@openvz.org>
 <20120825171605.GT23464@ZenIV.linux.org.uk>
 <20120825173958.GC19184@moon>
 <20120825175504.GU23464@ZenIV.linux.org.uk>
 <20120825185829.GE19184@moon>
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On Sat, Aug 25, 2012 at 10:58:29PM +0400, Cyrill Gorcunov wrote:
> On Sat, Aug 25, 2012 at 06:55:04PM +0100, Al Viro wrote:
> > > Well, this could be simplified indeed, if I understand you correctly
> > > you propose just save f_mode in flexible array and use it instead
> > > of struct file, right? (which will require to rewrite code a bit)
> > 
> > Yes.  FWIW, proc_fill_cache() is really atrocious ;-/  Not to mention
> 
> OK, thanks. I'm putting this cleanup task in my big todo list. Hope I'll
> manage on the next week with it.
> 
> > anything else, if we ever get a negative dentry there, we have a dentry
> > leak.  I don't think it's possible in practice, but...  Furthermore,
> 
> could you please elaborate, you mean this string?

I mean that if we get to that if (... || !child->d_inode) and end up
evaluating the last part at all, we have acquired a reference to that
struct dentry.  And if that last part ends up being true (i.e. if it's
a negative dentry), we'll return from function without having dropped
the reference we'd acquired.
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