From: Willem de Bruijn Date: Tue, 8 Mar 2016 20:18:54 +0000 (-0500) Subject: macvtap: always pass ethernet header in linear X-Git-Tag: v4.6-rc1~91^2~86 X-Git-Url: http://git.cascardo.info/?p=cascardo%2Flinux.git;a=commitdiff_plain;h=8e2ad4113ce4671686740f808ff2795395c39eef 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 Signed-off-by: David S. Miller --- diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index d636d051fac8..95394edd1ed5 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -760,6 +760,8 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, 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 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, 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,