diff options
authorMarcelo Leitner <mleitner@redhat.com>2015-02-23 11:17:13 -0300
committerBen Hutchings <ben@decadent.org.uk>2015-10-13 03:46:11 +0100
commit1c825dacb615430cb384e0e3be07700013291742 (patch)
parent06f0f9d843af52573c7dad0d81ee9df984e0b6be (diff)
ipv6: addrconf: validate new MTU before applying it
commit 77751427a1ff25b27d47a4c36b12c3c8667855ac upstream. 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 <mleitner@redhat.com> Signed-off-by: Sabrina Dubroca <sd@queasysnail.net> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
1 files changed, 16 insertions, 1 deletions
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 3afdd78..006867d 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4321,6 +4321,21 @@ int addrconf_sysctl_forward(ctl_table *ctl, int write,
return ret;
+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)
if (!idev || !idev->dev)
@@ -4421,7 +4436,7 @@ 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",