2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------
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@xxxxxxxxxx>
Signed-off-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 2.6.32:
- Add a strategy for the sysctl as we don't get a default strategy
- Adjust context, spacing]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
net/ipv6/addrconf.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index e8c4fd9..34eed01 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4036,6 +4036,40 @@ static int addrconf_sysctl_forward_strategy(ctl_table *table,
return addrconf_fixup_forwarding(table, valp, val);
}
+static
+struct ctl_table *addrconf_sysctl_mtu_init(struct ctl_table *newctl,
+ const struct ctl_table *ctl)
+{
+ struct inet6_dev *idev = ctl->extra1;
+ static int min_mtu = IPV6_MIN_MTU;
+
+ *newctl = *ctl;
+ newctl->extra1 = &min_mtu;
+ newctl->extra2 = idev ? &idev->dev->mtu : NULL;
+ return newctl;
+}
+
+static
+int addrconf_sysctl_mtu(struct ctl_table *ctl, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table lctl;
+
+ return proc_dointvec_minmax(addrconf_sysctl_mtu_init(&lctl, ctl),
+ write, buffer, lenp, ppos);
+}
+
+static int addrconf_sysctl_mtu_strategy(struct ctl_table *ctl,
+ void __user *oldval,
+ size_t __user *oldlenp,
+ void __user *newval, size_t newlen)
+{
+ struct ctl_table lctl;
+
+ return sysctl_intvec(addrconf_sysctl_mtu_init(&lctl, ctl),
+ oldval, oldlenp, newval, newlen);
+}
+
static void dev_disable_change(struct inet6_dev *idev)
{
if (!idev || !idev->dev)
@@ -4142,7 +4176,8 @@ static struct addrconf_sysctl_table
.data = &ipv6_devconf.mtu6,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = addrconf_sysctl_mtu,
+ .strategy = addrconf_sysctl_mtu_strategy,
},
{
.ctl_name = NET_IPV6_ACCEPT_RA,
--
1.7.12.2.21.g234cd45.dirty
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