macvtap: always pass ethernet header in linear
The stack expects link layer headers in the skb linear section.
Macvtap can create skbs with llheader in frags in edge cases:
when (IFF_VNET_HDR is off or vnet_hdr.hdr_len < ETH_HLEN) and
prepad + len > PAGE_SIZE and vnet_hdr.flags has no or bad csum.
Add checks to ensure linear is always at least ETH_HLEN.
At this point, len is already ensured to be >= ETH_HLEN.
For backwards compatiblity, rounds up short vnet_hdr.hdr_len.
This differs from tap and packet, which return an error.
Fixes b9fb9ee07e67 ("macvtap: add GSO/csum offload support")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index d636d05..95394ed 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -760,6 +760,8 @@
macvtap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
if (copylen > good_linear)
copylen = good_linear;
+ else if (copylen < ETH_HLEN)
+ copylen = ETH_HLEN;
linear = copylen;
i = *from;
iov_iter_advance(&i, copylen);
@@ -769,10 +771,11 @@
if (!zerocopy) {
copylen = len;
- if (macvtap16_to_cpu(q, vnet_hdr.hdr_len) > good_linear)
+ linear = macvtap16_to_cpu(q, vnet_hdr.hdr_len);
+ if (linear > good_linear)
linear = good_linear;
- else
- linear = macvtap16_to_cpu(q, vnet_hdr.hdr_len);
+ else if (linear < ETH_HLEN)
+ linear = ETH_HLEN;
}
skb = macvtap_alloc_skb(&q->sk, MACVTAP_RESERVE, copylen,