Cited commit added 'DEVLINK_CMD_PARAM_DEL' notifications whenever the
network namespace of the devlink instance is changed. Specifically, the
notifications are generated after calling reload_down(), but before
calling reload_up(). At this stage, the data structures accessed while
reading the value of the "acl_region_rehash_interval" devlink parameter
are uninitialized, resulting in a use-after-free [1].

Fix by moving the registration and unregistration of the devlink
parameter to the TCAM code where it is actually used. This means that
the parameter is unregistered during reload_down() and then
re-registered during reload_up(), avoiding the use-after-free between
these two operations.

Reproducer:

 # ip netns add test123
 # devlink dev reload pci/0000:06:00.0 netns test123

[1]
BUG: KASAN: use-after-free in mlxsw_sp_acl_tcam_vregion_rehash_intrvl_get+0xb2/0xd0
Read of size 4 at addr ffff888162fd37d8 by task devlink/1323
[...]
Call Trace:
 <TASK>
 dump_stack_lvl+0x95/0xbd
 print_report+0x181/0x4a1
 kasan_report+0xdb/0x200
 mlxsw_sp_acl_tcam_vregion_rehash_intrvl_get+0xb2/0xd0
 mlxsw_sp_params_acl_region_rehash_intrvl_get+0x32/0x80
 devlink_nl_param_fill.constprop.0+0x29a/0x11e0
 devlink_param_notify.constprop.0+0xb9/0x250
 devlink_notify_unregister+0xbc/0x470
 devlink_reload+0x1aa/0x440
 devlink_nl_cmd_reload+0x559/0x11b0
 genl_family_rcv_msg_doit.isra.0+0x1f8/0x2e0
 genl_rcv_msg+0x558/0x7f0
 netlink_rcv_skb+0x170/0x440
 genl_rcv+0x2d/0x40
 netlink_unicast+0x53f/0x810
 netlink_sendmsg+0x961/0xe80
 __sys_sendto+0x2a4/0x420
 __x64_sys_sendto+0xe5/0x1c0
 do_syscall_64+0x38/0x80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 7d7e9169 ("devlink: move devlink reload notifications back in between _down() and _up() calls")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>