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From: Richard Weinberger <richard@nod.at>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fs: Detect API misuse of i_op->lookup
Date: Sun, 25 Jan 2015 23:20:53 +0100	[thread overview]
Message-ID: <54C56C45.6060802@nod.at> (raw)
In-Reply-To: <20150125221643.GK29656@ZenIV.linux.org.uk>

Am 25.01.2015 um 23:16 schrieb Al Viro:
> On Sun, Jan 25, 2015 at 10:57:40PM +0100, Richard Weinberger wrote:
>> Hunting down a refcount issue in an out-of-tree filesystem uncovered
>> that its lookup function directly returned the dentry which was passed to it.
>> Add a BUG_ON() to detect such misuse in future.
> 
> In principle, it's not a bug.  You *must* grab a reference to dentry before
> returning it, but you can very well decide to return the one you've got -
> any place where have ->lookup() return NULL has every right to become
> return dget(dentry).

Thanks for the clarification! The filesystem in question did of course
not grab a reference before returning the same dentry.

Thanks,
//richard

      reply	other threads:[~2015-01-25 22:20 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-25 21:57 [PATCH] fs: Detect API misuse of i_op->lookup Richard Weinberger
2015-01-25 22:16 ` Al Viro
2015-01-25 22:20   ` Richard Weinberger [this message]

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