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

From: Matthias Kaehlcke
Date: Mon Mar 27 2017 - 15:59:42 EST


__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++;
}
}

--
2.12.1.578.ge9c3154ca4-goog