linux-kernel - Re: [PATCH] ovl: check dentry positiveness in ovl_cleanup

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Message-ID: <CAJfpeguUXTB5FVgbCMB+cRSbB4xkd06zPm-STc391yDXM7JQ5g@mail.gmail.com>
Date:	Wed, 9 Dec 2015 22:51:34 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:	David Howells <dhowells@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable@...r.kernel.org,
	"linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>
Subject: Re: [PATCH] ovl: check dentry positiveness in ovl_cleanup_whiteouts()

On Mon, Nov 16, 2015 at 4:44 PM, Konstantin Khlebnikov
<khlebnikov@...dex-team.ru> wrote:
> This patch fixes kernel crash at removing directory which contains
> whiteouts from lower layers.
>
> Cache of directory content passed as "list" contains entries from all
> layers, including whiteouts from lower layers. So, lookup in upper dir
> (moved into work at this stage) will return negative entry. Plus this
> cache is filled long before and we can race with external removal.
>
> Example:
>  mkdir -p lower0/dir lower1/dir upper work overlay
>  touch lower0/dir/a lower0/dir/b
>  mknod lower1/dir/a c 0 0
>  mount -t overlay none overlay -o lowerdir=lower1:lower0,upperdir=upper,workdir=work
>  rm -fr overlay/dir
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> Cc: Stable <stable@...r.kernel.org> # 3.18+

Thanks, applied.

Miklos
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