Re: tun issue after e0b46d0ee9c: tun: Use iovec iterators

[Jason Wang <jasowang@redhat.com>]

On Sun, Nov 30, 2014 at 6:03 PM, Herbert Xu 
<herbert@gondor.apana.org.au> wrote:
> On Sat, Nov 29, 2014 at 07:59:35AM +0800, Herbert Xu wrote:
>>  On Fri, Nov 28, 2014 at 05:25:27PM -0200, Marcelo Ricardo Leitner 
>> wrote:
>>  > 
>>  > I saw there are tun updates on Dave's queue but none seemed to 
>> handle this.
>>  > 
>>  > I can't use current net-next
>>  > (799d2fff1858004526ad75d66a5dd8a5cce6ad40) on a kvm hypervisor
>>  > because tun got clogged somehow. Bisected down to:
>>  > 
>>  > commit e0b46d0ee9c240c7430a47e9b0365674d4a04522
>>  > Author: Herbert Xu <herbert@gondor.apana.org.au>
>>  > Date:   Fri Nov 7 21:22:23 2014 +0800
>>  
>>  Does this patch help?
> 
> Oops, there was an embarrassing typo in the patch which causes
> it to not even build.  Here is the corrected version.
> 
> -- >8 --
> Subject: tun: Fix GSO meta-data handling in tun_get_user
>     
> When we write the GSO meta-data in tun_get_user we end up advancing
> the IO vector twice, thus exhausting the user buffer before we can
> finish writing the packet.
>     
> Fixes: f5ff53b4d97c ("{macvtap,tun}_get_user(): switch to iov_iter")
> Reported-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 4b743c6..6d44da1 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1052,7 +1052,7 @@ static ssize_t tun_get_user(struct tun_struct 
> *tun, struct tun_file *tfile,
>  
>  		if (gso.hdr_len > len)
>  			return -EINVAL;
> -		iov_iter_advance(from, tun->vnet_hdr_sz);
> +		iov_iter_advance(from, tun->vnet_hdr_sz - sizeof(gso));
>  	}
>  
>  	if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {
> 

Acked-by: Jason Wang <jasowang@redhat.com>