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if_vxlan(4): Add checking for loops and nesting of tunnels

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User misconfiguration, either tunnel loops, or a large number of
different nested tunnels, can overflow the kernel stack. Prevent that
by using if_tunnel_check_nesting().

PR:		278394
Diagnosed by:	markj
Reviewed by:	kp
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D45197
This commit is contained in:
Zhenlei Huang 2024-05-20 20:14:07 +08:00
parent c7581d76a1
commit 93fbfef0b5
1 changed files with 23 additions and 0 deletions
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23
sys/net/if_vxlan.c
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@ -432,6 +432,21 @@ TUNABLE_INT("net.link.vxlan.legacy_port", &vxlan_legacy_port);
static int vxlan_reuse_port = 0;
TUNABLE_INT("net.link.vxlan.reuse_port", &vxlan_reuse_port);
/*
* This macro controls the default upper limitation on nesting of vxlan
* tunnels. By default it is 3, as the overhead of IPv6 vxlan tunnel is 70
* bytes, this will create at most 210 bytes overhead and the most inner
* tunnel's MTU will be 1290 which will meet IPv6 minimum MTU size 1280.
* Be careful to configure the tunnels when raising the limit. A large
* number of nested tunnels can introduce system crash.
*/
#ifndef MAX_VXLAN_NEST
#define MAX_VXLAN_NEST 3
#endif
static int max_vxlan_nesting = MAX_VXLAN_NEST;
SYSCTL_INT(_net_link_vxlan, OID_AUTO, max_nesting, CTLFLAG_RW,
&max_vxlan_nesting, 0, "Max nested tunnels");
/* Default maximum number of addresses in the forwarding table. */
#ifndef VXLAN_FTABLE_MAX
#define VXLAN_FTABLE_MAX 2000
@ -2721,6 +2736,7 @@ vxlan_encap6(struct vxlan_softc *sc, const union vxlan_sockaddr *fvxlsa,
#endif
}
#define MTAG_VXLAN_LOOP 0x7876706c /* vxlp */
static int
vxlan_transmit(struct ifnet *ifp, struct mbuf *m)
{
@ -2746,6 +2762,13 @@ vxlan_transmit(struct ifnet *ifp, struct mbuf *m)
m_freem(m);
return (ENETDOWN);
}
if (__predict_false(if_tunnel_check_nesting(ifp, m, MTAG_VXLAN_LOOP,
max_vxlan_nesting) != 0)) {
VXLAN_RUNLOCK(sc, &tracker);
m_freem(m);
if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
return (ELOOP);
}
if ((m->m_flags & (M_BCAST | M_MCAST)) == 0)
fe = vxlan_ftable_entry_lookup(sc, eh->ether_dhost);