Re: [PATCH v2] cfg80211: Fix array-bounds warning in fragment copy

From: Matthias Kaehlcke
Date: Mon Apr 10 2017 - 17:36:12 EST


El Mon, Mar 27, 2017 at 12:58:22PM -0700 Matthias Kaehlcke ha dit:

> __ieee80211_amsdu_copy_frag intentionally initializes a pointer to
> array[-1] to increment it later to valid values. clang rightfully
> generates an array-bounds warning on the initialization statement.
>
> Initialize the pointer to array[0] and change the algorithm from
> increment before to increment after consume.
>
> Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> ---
> net/wireless/util.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/wireless/util.c b/net/wireless/util.c
> index 68e5f2ecee1a..52795ae5337f 100644
> --- a/net/wireless/util.c
> +++ b/net/wireless/util.c
> @@ -659,7 +659,7 @@ __ieee80211_amsdu_copy_frag(struct sk_buff *skb, struct sk_buff *frame,
> int offset, int len)
> {
> struct skb_shared_info *sh = skb_shinfo(skb);
> - const skb_frag_t *frag = &sh->frags[-1];
> + const skb_frag_t *frag = &sh->frags[0];
> struct page *frag_page;
> void *frag_ptr;
> int frag_len, frag_size;
> @@ -672,10 +672,10 @@ __ieee80211_amsdu_copy_frag(struct sk_buff *skb, struct sk_buff *frame,
>
> while (offset >= frag_size) {
> offset -= frag_size;
> - frag++;
> frag_page = skb_frag_page(frag);
> frag_ptr = skb_frag_address(frag);
> frag_size = skb_frag_size(frag);
> + frag++;
> }
>
> frag_ptr += offset;
> @@ -687,12 +687,12 @@ __ieee80211_amsdu_copy_frag(struct sk_buff *skb, struct sk_buff *frame,
> len -= cur_len;
>
> while (len > 0) {
> - frag++;
> frag_len = skb_frag_size(frag);
> cur_len = min(len, frag_len);
> __frame_add_frag(frame, skb_frag_page(frag),
> skb_frag_address(frag), cur_len, frag_len);
> len -= cur_len;
> + frag++;
> }
> }
>

Ping, any feedback on this patch?

Thanks

Matthias