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

[Matthias Kaehlcke]

__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.
Work around this by initializing the pointer to array[0] and
decrementing it later, which allows to leave the rest of the
algorithm untouched.

Signed-off-by: Matthias Kaehlcke <m...@chromium.org>
---
 net/wireless/util.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/wireless/util.c b/net/wireless/util.c
index 68e5f2ecee1a..d3d459e4a070 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;
@@ -669,6 +669,7 @@ __ieee80211_amsdu_copy_frag(struct sk_buff *skb, struct 
sk_buff *frame,
        frag_page = virt_to_head_page(skb->head);
        frag_ptr = skb->data;
        frag_size = head_size;
+       frag--;
 
        while (offset >= frag_size) {
                offset -= frag_size;
-- 
2.12.1.578.ge9c3154ca4-goog