Subject: Re: [PATCH] macvtap: fix the uninitialized var using in macvtap_alloc_skb()

From: "Michael S. Tsirkin" <[email-masked]>
Date: Mon, 19 Sep 2011 12:54:15 +0300

On Mon, Sep 19, 2011 at 05:48:31PM +0800, Jason Wang wrote:
> Commit d1b08284 use new frag API but would leave f to be used
> uninitialized, this patch fix it.
> 
> Signed-off-by: Jason Wang <[email-masked]>

Good catch. Makes absolute sense.

Acked-by: Michael S. Tsirkin <[email-masked]>

> ---
>  drivers/net/macvtap.c |   12 +++++-------
>  1 files changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index 7c3f84a..3da5578 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -453,7 +453,6 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
>  	int copy = skb_headlen(skb);
>  	int size, offset1 = 0;
>  	int i = 0;
> -	skb_frag_t *f;
>  
>  	/* Skip over from offset */
>  	while (count && (offset >= from->iov_len)) {
> @@ -503,14 +502,13 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
>  		skb->truesize += len;
>  		atomic_add(len, &skb->sk->sk_wmem_alloc);
>  		while (len) {
> -			__skb_fill_page_desc(
> -				skb, i, page[i],
> -				base & ~PAGE_MASK,
> -				min_t(int, len, PAGE_SIZE - f->page_offset));
> +			int off = base & ~PAGE_MASK;
> +			int size = min_t(int, len, PAGE_SIZE - off);
> +			__skb_fill_page_desc(skb, i, page[i], off, size);
>  			skb_shinfo(skb)->nr_frags++;
>  			/* increase sk_wmem_alloc */
> -			base += f->size;
> -			len -= f->size;
> +			base += size;
> +			len -= size;
>  			i++;
>  		}
>  		offset1 = 0;