From 6e8e5d5dfee54ee385b40f4c7d1a945b2d32ab11 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 0f0f9ce3a7769..b181dfb3d6d60 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 c81680dc10eb7..293ce8dfc9e65 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 701408a1ded6b..58914c8ea68f8 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 8b2256e880e0e..0259b719bebf5 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 c69cd8721b284..a83375d3af72e 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 2568c449fe36c..bddc1dd2e7f22 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 4b70539199765..49ddca31c4daf 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 303012adf9e6e..af6be70821c49 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -738,7 +738,7 @@ drop: 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 191fc24a745a9..8f024d41eefa9 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 52271947a4713..3ec1f69c5ceb2 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -896,6 +896,8 @@ new_segment: 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 0905997e58733..492c7cfe14532 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 667a6adfccf89..367e2ec01da1f 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 f26f0da7f0957..d141fc32a2eab 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; -- 2.39.5