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Subject: Re: [PATCH] macvtap: fix TUNSETSNDBUF values > 64k
To: "Michael S. Tsirkin" <mst@redhat.com>, linux-kernel@vger.kernel.org
References: <1442572808-6438-1-git-send-email-mst@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>,
        Matthew Rosato <mjrosato@linux.vnet.ibm.com>,
        Al Viro <viro@zeniv.linux.org.uk>, Jason Wang <jasowang@redhat.com>,
        David Gibson <david@gibson.dropbear.id.au>,
        Greg Kurz <gkurz@linux.vnet.ibm.com>,
        Vlad Yasevich <vyasevich@gmail.com>,
        Justin Cormack <justin@myriabit.com>,
        Herbert Xu <herbert@gondor.apana.org.au>, netdev@vger.kernel.org,
        Matthew Rosato <mjrosato@linux.vnet.ibm.com>
From: Christian Borntraeger <borntraeger@de.ibm.com>
Message-ID: <55FBEC23.8080409@de.ibm.com>
Date: Fri, 18 Sep 2015 12:49:07 +0200
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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@davemloft.net>
> Fixes: 39ec7de7092b ("macvtap: fix uninitialized access on TUNSETIFF")
> Reported-by: Mark A. Peloquin
> Bisected-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com>
> Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

You can add
Tested-by:  Matthew Rosato <mjrosato@linux.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@de.ibm.com>

what about
CC: stable@vger.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:
>