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authorMarcelo Leitner <mleitner@redhat.com>2015-02-23 11:17:13 -0300
committerDavid S. Miller <davem@davemloft.net>2015-02-23 18:16:12 -0500
commit77751427a1ff25b27d47a4c36b12c3c8667855ac (patch)
treeaecd97232dd3fe3977adcef402ea3be1b60eeef9 /net
parent8d4ac39df09c6f8078af60cd0ddd7b2435728e72 (diff)
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 <mleitner@redhat.com> Signed-off-by: Sabrina Dubroca <sd@queasysnail.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv6/addrconf.c17
1 files changed, 16 insertions, 1 deletions
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",