linux-kernel - Re: [PATCH] macvtap: fix TUNSETSNDBUF values

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Message-ID: <55FBEC23.8080409@de.ibm.com>
Date:	Fri, 18 Sep 2015 12:49:07 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
Cc:	"David S. Miller" <davem@...emloft.net>,
	Matthew Rosato <mjrosato@...ux.vnet.ibm.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Jason Wang <jasowang@...hat.com>,
	David Gibson <david@...son.dropbear.id.au>,
	Greg Kurz <gkurz@...ux.vnet.ibm.com>,
	Vlad Yasevich <vyasevich@...il.com>,
	Justin Cormack <justin@...iabit.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	netdev@...r.kernel.org,
	Matthew Rosato <mjrosato@...ux.vnet.ibm.com>
Subject: Re: [PATCH] macvtap: fix TUNSETSNDBUF values > 64k

Am 18.09.2015 um 12:41 schrieb Michael S. Tsirkin:
> Upon TUNSETSNDBUF,  macvtap reads the requested sndbuf size into
> a local variable u.
> commit 39ec7de7092b ("macvtap: fix uninitialized access on
> TUNSETIFF") changed its type to u16 (which is the right thing to
> do for all other macvtap ioctls), breaking all values > 64k.
> 
> The value of TUNSETSNDBUF is actually a signed 32 bit integer, so
> the right thing to do is to read it into an int.
> 
> Cc: David S. Miller <davem@...emloft.net>
> Fixes: 39ec7de7092b ("macvtap: fix uninitialized access on TUNSETIFF")
> Reported-by: Mark A. Peloquin
> Bisected-by: Matthew Rosato <mjrosato@...ux.vnet.ibm.com>
> Reported-by: Christian Borntraeger <borntraeger@...ibm.com>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

You can add
Tested-by:  Matthew Rosato <mjrosato@...ux.vnet.ibm.com>
as this looks identical to an early version of my patch which was tested,
by Matt. (I send you the other version that changes back u as I felt that
u and up are named to identify unsigned)

and please add
Acked-by: Christian Borntraeger <borntraeger@...ibm.com>

what about
CC: stable@...r.kernel.org

Christian

> ---
> 
> This patch probably makes sense on stable.
> 
>  drivers/net/macvtap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index edd7734..248478c 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -1111,10 +1111,10 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
>  		return 0;
> 
>  	case TUNSETSNDBUF:
> -		if (get_user(u, up))
> +		if (get_user(s, sp))
>  			return -EFAULT;
> 
> -		q->sk.sk_sndbuf = u;
> +		q->sk.sk_sndbuf = s;
>  		return 0;
> 
>  	case TUNGETVNETHDRSZ:
> 

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