Commit 8d609725 authored Nov 25, 2014 by Seth Forshee Committed by David S. Miller Dec 02, 2014

xen-netfront: Remove BUGs on paged skb data which crosses a page boundary



These BUGs can be erroneously triggered by frags which refer to
tail pages within a compound page. The data in these pages may
overrun the hardware page while still being contained within the
compound page, but since compound_order() evaluates to 0 for tail
pages the assertion fails. The code already iterates through
subsequent pages correctly in this scenario, so the BUGs are
unnecessary and can be removed.

Fixes: f36c3747 ("xen/netfront: handle compound page fragments on transmit")
Cc: <stable@vger.kernel.org> # 3.7+
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7fa2955f

drivers/net/xen-netfront.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -496,9 +496,6 @@ static void xennet_make_frags(struct sk_buff skb, struct netfront_queue queue,
		len = skb_frag_size(frag);
		offset = frag->page_offset;

		/* Data must not cross a page boundary. */
		BUG_ON(len + offset > PAGE_SIZE<<compound_order(page));

		/* Skip unused frames from start of page */
		page += offset >> PAGE_SHIFT;
		offset &= ~PAGE_MASK;
		@@ -506,8 +503,6 @@ static void xennet_make_frags(struct sk_buff skb, struct netfront_queue queue,
		while (len > 0) {
		unsigned long bytes;

		BUG_ON(offset >= PAGE_SIZE);

		bytes = PAGE_SIZE - offset;
		if (bytes > len)
		bytes = len;