ipv6: addrconf: validate new MTU before applying it

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commit 77751427a1 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>
Cc: Moritz Muehlenhoff <jmm@debian.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

...

This commit is contained in:

Marcelo Leitner 2015-02-23 11:17:13 -03:00 • committed by Luis Henriques

parent 76aee4f56f

commit fd0ad1be8d

1 changed files with 16 additions and 1 deletions

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net/ipv6/addrconf.c

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