@@ -9,6 +9,7 @@
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
+#include <linux/if_arp.h>
#include <linux/rtnetlink.h>
#include <linux/llc.h>
#include <linux/slab.h>
@@ -574,6 +575,10 @@ int garp_init_applicant(struct net_device *dev, struct garp_application *appl)
ASSERT_RTNL();
+ err = -EINVAL;
+ if (dev->type != ARPHRD_ETHER)
+ goto err1;
+
if (!rtnl_dereference(dev->garp_port)) {
err = garp_init_port(dev);
if (err < 0)
@@ -12,6 +12,7 @@
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
+#include <linux/if_arp.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <linux/module.h>
@@ -859,6 +860,10 @@ int mrp_init_applicant(struct net_device *dev, struct mrp_application *appl)
ASSERT_RTNL();
+ err = -EINVAL;
+ if (dev->type != ARPHRD_ETHER)
+ goto err1;
+
if (!rtnl_dereference(dev->mrp_port)) {
err = mrp_init_port(dev);
if (err < 0)
When creating a VLAN device, we initialize GARP (garp_init_applicant) and MRP (mrp_init_applicant) for the underlying device. As part of the initialization process, we add the multicast address of each applicant to the underlying device, by calling dev_mc_add. __dev_mc_add uses dev->addr_len to determine the length of the new multicast address. This causes an out-of-bounds read if dev->addr_len is greater than 6, since the multicast addresses provided by GARP and MRP are only 6 bytes long. This behaviour can be reproduced using the following commands: ip tunnel add gretest mode ip6gre local ::1 remote ::2 dev lo ip l set up dev gretest ip link add link gretest name vlantest type vlan id 100 Then, the following command will display the address of garp_pdu_rcv: ip maddr show | grep 01:80:c2:00:00:21 Fix this by enforcing the type of the underlying device during GARP and MRP initialization. Fixes: 22bedad3ce11 ("net: convert multicast list to list_head") Reported-by: syzbot <syzbot+91161fe81857b396c8a0@syzkaller.appspotmail.com> Closes: https://lore.kernel.org/netdev/000000000000ca9a81061a01ec20@google.com/ Signed-off-by: Oscar Maes <oscmaes92@gmail.com> --- net/802/garp.c | 5 +++++ net/802/mrp.c | 5 +++++ 2 files changed, 10 insertions(+)