From cef401de7be8c4e155c6746bfccf721a4fa5fab9 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 25 Jan 2013 20:34:37 +0000 Subject: [PATCH] net: fix possible wrong checksum generation Pravin Shelar mentioned that GSO could potentially generate wrong TX checksum if skb has fragments that are overwritten by the user between the checksum computation and transmit. He suggested to linearize skbs but this extra copy can be avoided for normal tcp skbs cooked by tcp_sendmsg(). This patch introduces a new SKB_GSO_SHARED_FRAG flag, set in skb_shinfo(skb)->gso_type if at least one frag can be modified by the user. Typical sources of such possible overwrites are {vm}splice(), sendfile(), and macvtap/tun/virtio_net drivers. Tested: $ netperf -H 7.7.8.84 MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 7.7.8.84 () port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 16384 10.00 3959.52 $ netperf -H 7.7.8.84 -t TCP_SENDFILE TCP SENDFILE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 7.7.8.84 () port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 16384 10.00 3216.80 Performance of the SENDFILE is impacted by the extra allocation and copy, and because we use order-0 pages, while the TCP_STREAM uses bigger pages. Reported-by: Pravin Shelar Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- drivers/net/macvtap.c | 3 ++- drivers/net/tun.c | 12 ++++++++---- drivers/net/virtio_net.c | 12 ++++++++---- include/linux/skbuff.h | 19 +++++++++++++++++++ net/core/dev.c | 9 +++++++++ net/core/skbuff.c | 4 ++++ net/ipv4/af_inet.c | 1 + net/ipv4/ip_gre.c | 4 +++- net/ipv4/ipip.c | 4 +++- net/ipv4/tcp.c | 3 +++ net/ipv4/tcp_input.c | 4 ++-- net/ipv4/tcp_output.c | 4 ++-- net/ipv6/ip6_offload.c | 1 + 13 files changed, 65 insertions(+), 15 deletions(-) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 0f0f9ce3a776..b181dfb3d6d6 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -543,6 +543,7 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from, skb->data_len += len; skb->len += len; skb->truesize += truesize; + skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG; atomic_add(truesize, &skb->sk->sk_wmem_alloc); while (len) { int off = base & ~PAGE_MASK; @@ -598,7 +599,7 @@ static int macvtap_skb_from_vnet_hdr(struct sk_buff *skb, if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) { skb_shinfo(skb)->gso_size = vnet_hdr->gso_size; - skb_shinfo(skb)->gso_type = gso_type; + skb_shinfo(skb)->gso_type |= gso_type; /* Header must be checked, and gso_segs computed. */ skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY; diff --git a/drivers/net/tun.c b/drivers/net/tun.c index c81680dc10eb..293ce8dfc9e6 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1005,6 +1005,7 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from, skb->data_len += len; skb->len += len; skb->truesize += truesize; + skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG; atomic_add(truesize, &skb->sk->sk_wmem_alloc); while (len) { int off = base & ~PAGE_MASK; @@ -1150,16 +1151,18 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, } if (gso.gso_type != VIRTIO_NET_HDR_GSO_NONE) { + unsigned short gso_type = 0; + pr_debug("GSO!\n"); switch (gso.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) { case VIRTIO_NET_HDR_GSO_TCPV4: - skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4; + gso_type = SKB_GSO_TCPV4; break; case VIRTIO_NET_HDR_GSO_TCPV6: - skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6; + gso_type = SKB_GSO_TCPV6; break; case VIRTIO_NET_HDR_GSO_UDP: - skb_shinfo(skb)->gso_type = SKB_GSO_UDP; + gso_type = SKB_GSO_UDP; break; default: tun->dev->stats.rx_frame_errors++; @@ -1168,9 +1171,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, } if (gso.gso_type & VIRTIO_NET_HDR_GSO_ECN) - skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; + gso_type |= SKB_GSO_TCP_ECN; skb_shinfo(skb)->gso_size = gso.gso_size; + skb_shinfo(skb)->gso_type |= gso_type; if (skb_shinfo(skb)->gso_size == 0) { tun->dev->stats.rx_frame_errors++; kfree_skb(skb); diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 701408a1ded6..58914c8ea68f 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -220,6 +220,7 @@ static void set_skb_frag(struct sk_buff *skb, struct page *page, skb->len += size; skb->truesize += PAGE_SIZE; skb_shinfo(skb)->nr_frags++; + skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG; *len -= size; } @@ -379,16 +380,18 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len) ntohs(skb->protocol), skb->len, skb->pkt_type); if (hdr->hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) { + unsigned short gso_type = 0; + pr_debug("GSO!\n"); switch (hdr->hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) { case VIRTIO_NET_HDR_GSO_TCPV4: - skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4; + gso_type = SKB_GSO_TCPV4; break; case VIRTIO_NET_HDR_GSO_UDP: - skb_shinfo(skb)->gso_type = SKB_GSO_UDP; + gso_type = SKB_GSO_UDP; break; case VIRTIO_NET_HDR_GSO_TCPV6: - skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6; + gso_type = SKB_GSO_TCPV6; break; default: net_warn_ratelimited("%s: bad gso type %u.\n", @@ -397,7 +400,7 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len) } if (hdr->hdr.gso_type & VIRTIO_NET_HDR_GSO_ECN) - skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; + gso_type |= SKB_GSO_TCP_ECN; skb_shinfo(skb)->gso_size = hdr->hdr.gso_size; if (skb_shinfo(skb)->gso_size == 0) { @@ -405,6 +408,7 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len) goto frame_err; } + skb_shinfo(skb)->gso_type |= gso_type; /* Header must be checked, and gso_segs computed. */ skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY; skb_shinfo(skb)->gso_segs = 0; diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 8b2256e880e0..0259b719bebf 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -307,6 +307,13 @@ enum { SKB_GSO_TCPV6 = 1 << 4, SKB_GSO_FCOE = 1 << 5, + + /* This indicates at least one fragment might be overwritten + * (as in vmsplice(), sendfile() ...) + * If we need to compute a TX checksum, we'll need to copy + * all frags to avoid possible bad checksum + */ + SKB_GSO_SHARED_FRAG = 1 << 6, }; #if BITS_PER_LONG > 32 @@ -2200,6 +2207,18 @@ static inline int skb_linearize(struct sk_buff *skb) return skb_is_nonlinear(skb) ? __skb_linearize(skb) : 0; } +/** + * skb_has_shared_frag - can any frag be overwritten + * @skb: buffer to test + * + * Return true if the skb has at least one frag that might be modified + * by an external entity (as in vmsplice()/sendfile()) + */ +static inline bool skb_has_shared_frag(const struct sk_buff *skb) +{ + return skb_shinfo(skb)->gso_type & SKB_GSO_SHARED_FRAG; +} + /** * skb_linearize_cow - make sure skb is linear and writable * @skb: buffer to process diff --git a/net/core/dev.c b/net/core/dev.c index c69cd8721b28..a83375d3af72 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2271,6 +2271,15 @@ int skb_checksum_help(struct sk_buff *skb) return -EINVAL; } + /* Before computing a checksum, we should make sure no frag could + * be modified by an external entity : checksum could be wrong. + */ + if (skb_has_shared_frag(skb)) { + ret = __skb_linearize(skb); + if (ret) + goto out; + } + offset = skb_checksum_start_offset(skb); BUG_ON(offset >= skb_headlen(skb)); csum = skb_checksum(skb, offset, skb->len - offset, 0); diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 2568c449fe36..bddc1dd2e7f2 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2340,6 +2340,8 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len) { int pos = skb_headlen(skb); + skb_shinfo(skb1)->gso_type = skb_shinfo(skb)->gso_type; + if (len < pos) /* Split line is inside header. */ skb_split_inside_header(skb, skb1, len, pos); else /* Second chunk has no header, nothing to copy. */ @@ -2845,6 +2847,8 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features) skb_copy_from_linear_data_offset(skb, offset, skb_put(nskb, hsize), hsize); + skb_shinfo(nskb)->gso_type = skb_shinfo(skb)->gso_type; + while (pos < offset + len && i < nfrags) { *frag = skb_shinfo(skb)->frags[i]; __skb_frag_ref(frag); diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 4b7053919976..49ddca31c4da 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1306,6 +1306,7 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb, SKB_GSO_UDP | SKB_GSO_DODGY | SKB_GSO_TCP_ECN | + SKB_GSO_SHARED_FRAG | 0))) goto out; diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 303012adf9e6..af6be70821c4 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -738,7 +738,7 @@ static int ipgre_rcv(struct sk_buff *skb) static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) { struct ip_tunnel *tunnel = netdev_priv(dev); - const struct iphdr *old_iph = ip_hdr(skb); + const struct iphdr *old_iph; const struct iphdr *tiph; struct flowi4 fl4; u8 tos; @@ -756,6 +756,8 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev skb_checksum_help(skb)) goto tx_error; + old_iph = ip_hdr(skb); + if (dev->type == ARPHRD_ETHER) IPCB(skb)->flags = 0; diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c index 191fc24a745a..8f024d41eefa 100644 --- a/net/ipv4/ipip.c +++ b/net/ipv4/ipip.c @@ -472,7 +472,7 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) __be16 df = tiph->frag_off; struct rtable *rt; /* Route to the other host */ struct net_device *tdev; /* Device to other host */ - const struct iphdr *old_iph = ip_hdr(skb); + const struct iphdr *old_iph; struct iphdr *iph; /* Our new IP header */ unsigned int max_headroom; /* The extra header space needed */ __be32 dst = tiph->daddr; @@ -486,6 +486,8 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) skb_checksum_help(skb)) goto tx_error; + old_iph = ip_hdr(skb); + if (tos & 1) tos = old_iph->tos; diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 52271947a471..3ec1f69c5ceb 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -896,6 +896,8 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset, skb_fill_page_desc(skb, i, page, offset, copy); } + skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG; + skb->len += copy; skb->data_len += copy; skb->truesize += copy; @@ -3032,6 +3034,7 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, SKB_GSO_DODGY | SKB_GSO_TCP_ECN | SKB_GSO_TCPV6 | + SKB_GSO_SHARED_FRAG | 0) || !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))) goto out; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 0905997e5873..492c7cfe1453 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1240,13 +1240,13 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, */ if (!skb_shinfo(prev)->gso_size) { skb_shinfo(prev)->gso_size = mss; - skb_shinfo(prev)->gso_type = sk->sk_gso_type; + skb_shinfo(prev)->gso_type |= sk->sk_gso_type; } /* CHECKME: To clear or not to clear? Mimics normal skb currently */ if (skb_shinfo(skb)->gso_segs <= 1) { skb_shinfo(skb)->gso_size = 0; - skb_shinfo(skb)->gso_type = 0; + skb_shinfo(skb)->gso_type &= SKB_GSO_SHARED_FRAG; } /* Difference in this won't matter, both ACKed by the same cumul. ACK */ diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 667a6adfccf8..367e2ec01da1 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1133,6 +1133,7 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb, unsigned int mss_now) { + skb_shinfo(skb)->gso_type &= SKB_GSO_SHARED_FRAG; if (skb->len <= mss_now || !sk_can_gso(sk) || skb->ip_summed == CHECKSUM_NONE) { /* Avoid the costly divide in the normal @@ -1140,11 +1141,10 @@ static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb, */ skb_shinfo(skb)->gso_segs = 1; skb_shinfo(skb)->gso_size = 0; - skb_shinfo(skb)->gso_type = 0; } else { skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now); skb_shinfo(skb)->gso_size = mss_now; - skb_shinfo(skb)->gso_type = sk->sk_gso_type; + skb_shinfo(skb)->gso_type |= sk->sk_gso_type; } } diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c index f26f0da7f095..d141fc32a2ea 100644 --- a/net/ipv6/ip6_offload.c +++ b/net/ipv6/ip6_offload.c @@ -100,6 +100,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb, SKB_GSO_DODGY | SKB_GSO_TCP_ECN | SKB_GSO_TCPV6 | + SKB_GSO_SHARED_FRAG | 0))) goto out;