From 77751427a1ff25b27d47a4c36b12c3c8667855ac Mon Sep 17 00:00:00 2001 From: Marcelo Leitner Date: Mon, 23 Feb 2015 11:17:13 -0300 Subject: ipv6: addrconf: validate new MTU before applying it Currently we don't check if the new MTU is valid or not and this allows one to configure a smaller than minimum allowed by RFCs or even bigger than interface own MTU, which is a problem as it may lead to packet drops. If you have a daemon like NetworkManager running, this may be exploited by remote attackers by forging RA packets with an invalid MTU, possibly leading to a DoS. (NetworkManager currently only validates for values too small, but not for too big ones.) The fix is just to make sure the new value is valid. That is, between IPV6_MIN_MTU and interface's MTU. Note that similar check is already performed at ndisc_router_discovery(), for when kernel itself parses the RA. Signed-off-by: Marcelo Ricardo Leitner Signed-off-by: Sabrina Dubroca Signed-off-by: David S. Miller --- net/ipv6/addrconf.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'net/ipv6') diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 98e4a63d72bb..b6030025f411 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -4903,6 +4903,21 @@ int addrconf_sysctl_forward(struct ctl_table *ctl, int write, return ret; } +static +int addrconf_sysctl_mtu(struct ctl_table *ctl, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + struct inet6_dev *idev = ctl->extra1; + int min_mtu = IPV6_MIN_MTU; + struct ctl_table lctl; + + lctl = *ctl; + lctl.extra1 = &min_mtu; + lctl.extra2 = idev ? &idev->dev->mtu : NULL; + + return proc_dointvec_minmax(&lctl, write, buffer, lenp, ppos); +} + static void dev_disable_change(struct inet6_dev *idev) { struct netdev_notifier_info info; @@ -5054,7 +5069,7 @@ static struct addrconf_sysctl_table .data = &ipv6_devconf.mtu6, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec, + .proc_handler = addrconf_sysctl_mtu, }, { .procname = "accept_ra", -- cgit v1.2.2 From acf8dd0a9d0b9e4cdb597c2f74802f79c699e802 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Michal=20Kube=C4=8Dek?= Date: Mon, 2 Mar 2015 18:27:11 +0100 Subject: udp: only allow UFO for packets from SOCK_DGRAM sockets If an over-MTU UDP datagram is sent through a SOCK_RAW socket to a UFO-capable device, ip_ufo_append_data() sets skb->ip_summed to CHECKSUM_PARTIAL unconditionally as all GSO code assumes transport layer checksum is to be computed on segmentation. However, in this case, skb->csum_start and skb->csum_offset are never set as raw socket transmit path bypasses udp_send_skb() where they are usually set. As a result, driver may access invalid memory when trying to calculate the checksum and store the result (as observed in virtio_net driver). Moreover, the very idea of modifying the userspace provided UDP header is IMHO against raw socket semantics (I wasn't able to find a document clearly stating this or the opposite, though). And while allowing CHECKSUM_NONE in the UFO case would be more efficient, it would be a bit too intrusive change just to handle a corner case like this. Therefore disallowing UFO for packets from SOCK_DGRAM seems to be the best option. Signed-off-by: Michal Kubecek Signed-off-by: David S. Miller --- net/ipv6/ip6_output.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/ipv6') diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 7deebf102cba..0a04a37305d5 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1298,7 +1298,8 @@ emsgsize: if (((length > mtu) || (skb && skb_is_gso(skb))) && (sk->sk_protocol == IPPROTO_UDP) && - (rt->dst.dev->features & NETIF_F_UFO)) { + (rt->dst.dev->features & NETIF_F_UFO) && + (sk->sk_type == SOCK_DGRAM)) { err = ip6_ufo_append_data(sk, queue, getfrag, from, length, hh_len, fragheaderlen, transhdrlen, mtu, flags, rt); -- cgit v1.2.2