[NET]: Revert sk_buff walker cleanups.
This reverts eefa3906283a2b60a6d02a2cda593a7d7d7946c5
The simplification made in that change works with the assumption that
the 'offset' parameter to these functions is always positive or zero,
which is not true. It can be and often is negative in order to access
SKB header values in front of skb->data.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/user_dma.c b/net/core/user_dma.c
index 89241cd..0ad1cd5 100644
--- a/net/core/user_dma.c
+++ b/net/core/user_dma.c
@@ -49,8 +49,8 @@
struct sk_buff *skb, int offset, struct iovec *to,
size_t len, struct dma_pinned_list *pinned_list)
{
- int end = skb_headlen(skb);
- int i, copy = end - offset;
+ int start = skb_headlen(skb);
+ int i, copy = start - offset;
dma_cookie_t cookie = 0;
/* Copy header. */
@@ -69,9 +69,11 @@
/* Copy paged appendix. Hmm... why does this look so complicated? */
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- BUG_TRAP(len >= 0);
+ int end;
- end = offset + skb_shinfo(skb)->frags[i].size;
+ BUG_TRAP(start <= offset + len);
+
+ end = start + skb_shinfo(skb)->frags[i].size;
copy = end - offset;
if ((copy = end - offset) > 0) {
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@@ -80,8 +82,8 @@
if (copy > len)
copy = len;
- cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list,
- page, frag->page_offset, copy);
+ cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,
+ frag->page_offset + offset - start, copy);
if (cookie < 0)
goto fault;
len -= copy;
@@ -89,21 +91,25 @@
goto end;
offset += copy;
}
+ start = end;
}
if (skb_shinfo(skb)->frag_list) {
struct sk_buff *list = skb_shinfo(skb)->frag_list;
for (; list; list = list->next) {
- BUG_TRAP(len >= 0);
+ int end;
- end = offset + list->len;
+ BUG_TRAP(start <= offset + len);
+
+ end = start + list->len;
copy = end - offset;
if (copy > 0) {
if (copy > len)
copy = len;
cookie = dma_skb_copy_datagram_iovec(chan, list,
- 0, to, copy, pinned_list);
+ offset - start, to, copy,
+ pinned_list);
if (cookie < 0)
goto fault;
len -= copy;
@@ -111,6 +117,7 @@
goto end;
offset += copy;
}
+ start = end;
}
}