Subject: Re: [PATCH 1/2] net: bonding: fix restricted __be16 degrades to integer

From: Jay Vosburgh <[email-masked]>
Date: Fri, 08 Mar 2019 12:54:46 -0800

Bo YU <[email-masked]> wrote:

>There are some warning when:
>
>sudo make C=1 CF=-D__CHECK_ENDIAN__ drivers/net/bonding/
>
>drivers/net/bonding/bond_main.c:2385:26: warning: restricted __be16 degrades to integer
>drivers/net/bonding/bond_main.c:2391:20: warning: restricted __be16 degrades to integer
>...
>drivers/net/bonding/bond_main.c:3241:60: warning: restricted __be16 degrades to integer
>drivers/net/bonding/bond_main.c:3241:60: warning: restricted __be16 degrades to integer
>
>So fix it.
>
>Signed-off-by: Bo YU <[email-masked]>
>---
> drivers/net/bonding/bond_main.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index b59708c35faf..135fec28daa9 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -2382,13 +2382,13 @@ static void bond_arp_send(struct net_device *slave_dev, int arp_op,
> 		return;
> 	}
> 
>-	if (!tags || tags->vlan_proto == VLAN_N_VID)
>+	if (!tags || be16_to_cpu(tags->vlan_proto) == VLAN_N_VID)
> 		goto xmit;
> 
> 	tags++;
> 
> 	/* Go through all the tags backwards and add them to the packet */
>-	while (tags->vlan_proto != VLAN_N_VID) {
>+	while (be16_to_cpu(tags->vlan_proto) != VLAN_N_VID) {

	I believe both of the above are incorrect, as vlan_proto is set
explicitly to VLAN_N_VID (in host byte order) by bond_verify_device_path
as a sentinel value.  Byte swapping the tags->vlan_proto value would
cause the test or loop to miss the sentinel.

> 		if (!tags->vlan_id) {
> 			tags++;
> 			continue;
>@@ -3238,7 +3238,7 @@ static inline u32 bond_eth_hash(struct sk_buff *skb)
> 
> 	ep = skb_header_pointer(skb, 0, sizeof(hdr_tmp), &hdr_tmp);
> 	if (ep)
>-		return ep->h_dest[5] ^ ep->h_source[5] ^ ep->h_proto;
>+		return ep->h_dest[5] ^ ep->h_source[5] ^ be16_to_cpu(ep->h_proto);

	This is probably harmless, other than adding work to the
transmit path.

	-J

---
	-Jay Vosburgh, [email-masked]