In the Linux kernel, the following vulnerability has been resolved:
mlxsw: spectrum_router: Fix use-after-free when deleting GRE net devices
The driver only offloads neighbors that are constructed on top of net devices registered by it or their uppers (which are all Ethernet). The device supports GRE encapsulation and decapsulation of forwarded traffic, but the driver will not offload dummy neighbors constructed on top of GRE net devices as they are not uppers of its net devices:
$ ip neigh show dev gre1 nud noarp 0.0.0.0 lladdr 0.0.0.0 NOARP
(Note that the neighbor is not marked with 'offload')
When the driver is reloaded and the existing configuration is replayed, the driver does not perform the same check regarding existing neighbors and offloads the previously added one:
$ ip neigh show dev gre1 nud noarp 0.0.0.0 lladdr 0.0.0.0 offload NOARP
If the neighbor is later deleted, the driver will ignore the notification (given the GRE net device is not its upper) and will therefore keep referencing freed memory, resulting in a use-after-free [1] when the net device is deleted:
Fix by skipping neighbor replay if the net device for which the replay is performed is not our upper.
[1] BUG: KASAN: slab-use-after-free in mlxsw_sp_neigh_entry_update+0x1ea/0x200 Read of size 8 at addr ffff888155b0e420 by task ip/2282 [...] Call Trace: <TASK> dump_stack_lvl+0x6f/0xa0 print_address_description.constprop.0+0x6f/0x350 print_report+0x108/0x205 kasan_report+0xdf/0x110 mlxsw_sp_neigh_entry_update+0x1ea/0x200 mlxsw_sp_router_rif_gone_sync+0x2a8/0x440 mlxsw_sp_rif_destroy+0x1e9/0x750 mlxsw_sp_netdevice_ipip_ol_event+0x3c9/0xdc0 mlxsw_sp_router_netdevice_event+0x3ac/0x15e0 notifier_call_chain+0xca/0x150...