linux-kernel - Re: [RFC PATCH] tun: don't zeroize sock->file on detach

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Date:	Thu, 19 Jul 2012 08:06:38 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stanislav Kinsbursky <skinsbursky@...allels.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	ruanzhijie@...mail.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] tun: don't zeroize sock->file on detach

On Wed, 2012-07-11 at 15:48 +0400, Stanislav Kinsbursky wrote:
> This is a fix for bug, introduced in 3.4 kernel by commit
> 1ab5ecb90cb6a3df1476e052f76a6e8f6511cb3d, which, among other things, replaced
> simple sock_put() by sk_release_kernel(). Below is sequence, which leads to
> oops for non-persistent devices:
> 
> tun_chr_close()
> tun_detach()				<== tun->socket.file = NULL
> tun_free_netdev()
> sk_release_sock()
> sock_release(sock->file == NULL)
> iput(SOCK_INODE(sock))			<== dereference on NULL pointer
> 
> This patch just removes zeroing of socket's file from __tun_detach().
> sock_release() will do this.
> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>
> ---
>  drivers/net/tun.c |    1 -
>  1 files changed, 0 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 987aeef..c1639f3 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -185,7 +185,6 @@ static void __tun_detach(struct tun_struct *tun)
>  	netif_tx_lock_bh(tun->dev);
>  	netif_carrier_off(tun->dev);
>  	tun->tfile = NULL;
> -	tun->socket.file = NULL;
>  	netif_tx_unlock_bh(tun->dev);
>  
>  	/* Drop read queue */
> 

Acked-by: Eric Dumazet <edumazet@...gle.com>

Thanks !


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