2025-06-18 09:28:27
Linux
PUBLISHED
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 link add name gre1 up type gre tos inherit local 192.0.2.1 remote 198.51.100.1
# ip neigh add 0.0.0.0 lladdr 0.0.0.0 nud noarp dev gre1
$ 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:
# devlink dev reload pci/0000:01:00.0
$ 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:
# ip neigh del 0.0.0.0 lladdr 0.0.0.0 dev gre1
# ip link del dev gre1
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: