In the Linux kernel, the following vulnerability has been resolved:
macvlan: fix error recovery in macvlan_common_newlink()
valis provided a nice repro to crash the kernel:
ip link add p1 type veth peer p2 ip link set address 00:00:00:00:00:20 dev p1 ip link set up dev p1 ip link set up dev p2
ip link add mv0 link p2 type macvlan mode source ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20
ping -c1 -I p1 1.2.3.4
He also gave a very detailed analysis:
<quote valis>
The issue is triggered when a new macvlan link is created with MACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or MACVLAN_MACADDR_SET) parameter, lower device already has a macvlan port and register_netdevice() called from macvlan_common_newlink() fails (e.g. because of the invalid link name).
In this case macvlan_hash_add_source is called from macvlan_change_sources() / macvlan_common_newlink():
This adds a reference to vlan to the port's vlan_source_hash using macvlan_source_entry.
vlan is a pointer to the priv data of the link that is being created.
When register_netdevice() fails, the error is returned from macvlan_newlink() to rtnl_newlink_create():
if (ops->newlink)
err = ops->newlink(dev, &params, extack);
else
err = register_netdevice(dev);
if (err < 0) {
free_netdev(dev);
goto out;
}
and free_netdev() is called, causing a kvfree() on the struct net_device that is still referenced in the source entry attached to the lower device's macvlan port.
Now all packets sent on the macvlan port with a matching source mac address will trigger a use-after-free in macvlan_forward_source().
</quote valis>
With all that, my fix is to make sure we call macvlan_flush_sources() regardless of @create value whenever "goto destroy_macvlan_port;" path is taken.
Many thanks to valis for following up on this issue.
| Software | From | Fixed in |
|---|---|---|
| linux / linux_kernel | 4.9.1 | 5.10.250 |
| linux / linux_kernel | 5.11 | 5.15.200 |
| linux / linux_kernel | 5.16 | 6.1.163 |
| linux / linux_kernel | 6.2 | 6.6.124 |
| linux / linux_kernel | 6.7 | 6.12.70 |
| linux / linux_kernel | 6.13 | 6.18.10 |
| linux / linux_kernel | 4.9 | 4.9.x |
| linux / linux_kernel | 4.9-rc6 | 4.9-rc6.x |
| linux / linux_kernel | 4.9-rc7 | 4.9-rc7.x |
| linux / linux_kernel | 4.9-rc8 | 4.9-rc8.x |
| linux / linux_kernel | 6.19-rc1 | 6.19-rc1.x |
| linux / linux_kernel | 6.19-rc2 | 6.19-rc2.x |
| linux / linux_kernel | 6.19-rc3 | 6.19-rc3.x |
| linux / linux_kernel | 6.19-rc4 | 6.19-rc4.x |
| linux / linux_kernel | 6.19-rc5 | 6.19-rc5.x |
| linux / linux_kernel | 6.19-rc6 | 6.19-rc6.x |
| linux / linux_kernel | 6.19-rc7 | 6.19-rc7.x |
| linux / linux_kernel | 6.19-rc8 | 6.19-rc8.x |
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