[PATCH] Fix AF_PACKET ABI breakage in 4.2

From: David Woodhouse
Date: Wed Sep 23 2015 - 10:44:40 EST


Commit 7d82410950aa ("virtio: add explicit big-endian support to memory
accessors") accidentally changed the virtio_net header used by
AF_PACKET with PACKET_VNET_HDR from host-endian to big-endian.

Since virtio_legacy_is_little_endian() is a very long identifier,
define a VIO_LE macro and use that throughout the code instead of the
hard-coded 'false' for little-endian.

This restores the ABI to match 4.1 and earlier kernels, and makes my
test program work again.

Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
---
Or perhaps we should just use (__force u16) and (__force __virtio16)
since that's all we really want anyway?

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 7b8e39a..d646623 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -230,6 +230,8 @@ struct packet_skb_cb {
} sa;
};

+#define VIO_LE virtio_legacy_is_little_endian()
+
#define PACKET_SKB_CB(__skb) ((struct packet_skb_cb *)((__skb)->cb))

#define GET_PBDQC_FROM_RB(x) ((struct tpacket_kbdq_core *)(&(x)->prb_bdqc))
@@ -2680,15 +2682,15 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
goto out_unlock;

if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
- (__virtio16_to_cpu(false, vnet_hdr.csum_start) +
- __virtio16_to_cpu(false, vnet_hdr.csum_offset) + 2 >
- __virtio16_to_cpu(false, vnet_hdr.hdr_len)))
- vnet_hdr.hdr_len = __cpu_to_virtio16(false,
- __virtio16_to_cpu(false, vnet_hdr.csum_start) +
- __virtio16_to_cpu(false, vnet_hdr.csum_offset) + 2);
+ (__virtio16_to_cpu(VIO_LE, vnet_hdr.csum_start) +
+ __virtio16_to_cpu(VIO_LE, vnet_hdr.csum_offset) + 2 >
+ __virtio16_to_cpu(VIO_LE, vnet_hdr.hdr_len)))
+ vnet_hdr.hdr_len = __cpu_to_virtio16(VIO_LE,
+ __virtio16_to_cpu(VIO_LE, vnet_hdr.csum_start) +
+ __virtio16_to_cpu(VIO_LE, vnet_hdr.csum_offset) + 2);

err = -EINVAL;
- if (__virtio16_to_cpu(false, vnet_hdr.hdr_len) > len)
+ if (__virtio16_to_cpu(VIO_LE, vnet_hdr.hdr_len) > len)
goto out_unlock;

if (vnet_hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
@@ -2731,7 +2733,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
hlen = LL_RESERVED_SPACE(dev);
tlen = dev->needed_tailroom;
skb = packet_alloc_skb(sk, hlen + tlen, hlen, len,
- __virtio16_to_cpu(false, vnet_hdr.hdr_len),
+ __virtio16_to_cpu(VIO_LE, vnet_hdr.hdr_len),
msg->msg_flags & MSG_DONTWAIT, &err);
if (skb == NULL)
goto out_unlock;
@@ -2778,8 +2780,8 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)

if (po->has_vnet_hdr) {
if (vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
- u16 s = __virtio16_to_cpu(false, vnet_hdr.csum_start);
- u16 o = __virtio16_to_cpu(false, vnet_hdr.csum_offset);
+ u16 s = __virtio16_to_cpu(VIO_LE, vnet_hdr.csum_start);
+ u16 o = __virtio16_to_cpu(VIO_LE, vnet_hdr.csum_offset);
if (!skb_partial_csum_set(skb, s, o)) {
err = -EINVAL;
goto out_free;
@@ -2787,7 +2789,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
}

skb_shinfo(skb)->gso_size =
- __virtio16_to_cpu(false, vnet_hdr.gso_size);
+ __virtio16_to_cpu(VIO_LE, vnet_hdr.gso_size);
skb_shinfo(skb)->gso_type = gso_type;

/* Header must be checked, and gso_segs computed. */
@@ -3161,9 +3163,9 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,

/* This is a hint as to how much should be linear. */
vnet_hdr.hdr_len =
- __cpu_to_virtio16(false, skb_headlen(skb));
+ __cpu_to_virtio16(VIO_LE, skb_headlen(skb));
vnet_hdr.gso_size =
- __cpu_to_virtio16(false, sinfo->gso_size);
+ __cpu_to_virtio16(VIO_LE, sinfo->gso_size);
if (sinfo->gso_type & SKB_GSO_TCPV4)
vnet_hdr.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
else if (sinfo->gso_type & SKB_GSO_TCPV6)
@@ -3181,9 +3183,9 @@ static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,

if (skb->ip_summed == CHECKSUM_PARTIAL) {
vnet_hdr.flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
- vnet_hdr.csum_start = __cpu_to_virtio16(false,
+ vnet_hdr.csum_start = __cpu_to_virtio16(VIO_LE,
skb_checksum_start_offset(skb));
- vnet_hdr.csum_offset = __cpu_to_virtio16(false,
+ vnet_hdr.csum_offset = __cpu_to_virtio16(VIO_LE,
skb->csum_offset);
} else if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
vnet_hdr.flags = VIRTIO_NET_HDR_F_DATA_VALID;

--
David Woodhouse Open Source Technology Centre
David.Woodhouse@xxxxxxxxx Intel Corporation

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