From 283c01d3fe7b9458e394155c2f9bb24c82524bde Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Tue, 8 Mar 2016 15:18:54 -0500 Subject: [PATCH] macvtap: always pass ethernet header in linear [ Upstream commit 8e2ad4113ce4671686740f808ff2795395c39eef ] 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 Signed-off-by: David S. Miller [bwh: Backported to 3.2: don't use macvtap16_to_cpu()] Signed-off-by: Ben Hutchings --- drivers/net/macvtap.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 7300447eb4c7..2fcdedefce42 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -720,6 +720,8 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, copylen = vnet_hdr.hdr_len ? vnet_hdr.hdr_len : GOODCOPY_LEN; if (copylen > good_linear) copylen = good_linear; + else if (copylen < ETH_HLEN) + copylen = ETH_HLEN; linear = copylen; if (iov_pages(iv, vnet_hdr_len + copylen, count) <= MAX_SKB_FRAGS) @@ -728,10 +730,11 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, if (!zerocopy) { copylen = len; - if (vnet_hdr.hdr_len > good_linear) + linear = vnet_hdr.hdr_len; + if (linear > good_linear) linear = good_linear; - else - linear = vnet_hdr.hdr_len; + else if (linear < ETH_HLEN) + linear = ETH_HLEN; } skb = macvtap_alloc_skb(&q->sk, MACVTAP_RESERVE, copylen, -- 2.39.2