linux-kernel - Re: [PATCH] ubifs: Fix inode leak in xattr code

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Message-ID: <a5e7b80e-e1db-7b57-3b94-4d8e3a43cc6a@nod.at>
Date:   Mon, 15 May 2017 17:22:49 +0200
From:   Richard Weinberger <richard@....at>
To:     dedekind1@...il.com, linux-mtd@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, adrian.hunter@...el.com,
        stable@...r.kernel.org
Subject: Re: [PATCH] ubifs: Fix inode leak in xattr code

Artem,

Am 15.05.2017 um 16:53 schrieb Artem Bityutskiy:
> On Mon, 2017-05-15 at 16:20 +0200, Richard Weinberger wrote:
>> To solve this problem, set i_nlink for all xattr inodes to 0, such
>> that
>> the iput() in the UBIFS xattr code makes the temporary inode vanish
>> immediately.
> 
> What if there is iget right after iput? With this patch, will we need
> to go all the way to the slow media instead of just getting having the
> inode from the inode cache?

Hmm, why would we go down to the slow media?
Since the xattr was just looked up there is a high chance that the TNC
will still contain the node.
A new inode needs to be allocated, though.

Alternatively we could add a iget_locked/drop_nlink/iput sequence to
ubifs_tnc_remove_ino(). But that will make unlink() much slower for files
that contain xattrs.

Thanks,
//richard