[PATCH 5.10 33/43] net: dsa: clear devlink port type before unregistering slave netdevs

Greg Kroah-Hartman
2021-01-22T14:48:25Z

From: Vladimir Oltean <vladimir.oltean@nxp.com>

[ Upstream commit 91158e1680b164c8d101144ca916a3dca10c3e17 ]

Florian reported a use-after-free bug in devlink_nl_port_fill found with
KASAN:

(devlink_nl_port_fill)
(devlink_port_notify)
(devlink_port_unregister)
(dsa_switch_teardown.part.3)
(dsa_tree_teardown_switches)
(dsa_unregister_switch)
(bcm_sf2_sw_remove)
(platform_remove)
(device_release_driver_internal)
(device_links_unbind_consumers)
(device_release_driver_internal)
(device_driver_detach)
(unbind_store)

Allocated by task 31:
alloc_netdev_mqs+0x5c/0x50c
dsa_slave_create+0x110/0x9c8
dsa_register_switch+0xdb0/0x13a4
b53_switch_register+0x47c/0x6dc
bcm_sf2_sw_probe+0xaa4/0xc98
platform_probe+0x90/0xf4
really_probe+0x184/0x728
driver_probe_device+0xa4/0x278
__device_attach_driver+0xe8/0x148
bus_for_each_drv+0x108/0x158

Freed by task 249:
free_netdev+0x170/0x194
dsa_slave_destroy+0xac/0xb0
dsa_port_teardown.part.2+0xa0/0xb4
dsa_tree_teardown_switches+0x50/0xc4
dsa_unregister_switch+0x124/0x250
bcm_sf2_sw_remove+0x98/0x13c
platform_remove+0x44/0x5c
device_release_driver_internal+0x150/0x254
device_links_unbind_consumers+0xf8/0x12c
device_release_driver_internal+0x84/0x254
device_driver_detach+0x30/0x34
unbind_store+0x90/0x134

What happens is that devlink_port_unregister emits a netlink
DEVLINK_CMD_PORT_DEL message which associates the devlink port that is
getting unregistered with the ifindex of its corresponding net_device.
Only trouble is, the net_device has already been unregistered.

It looks like we can stub out the search for a corresponding net_device
if we clear the devlink_port's type. This looks like a bit of a hack,
but also seems to be the reason why the devlink_port_type_clear function
exists in the first place.

Fixes: 3122433eb533 ("net: dsa: Register devlink ports before calling DSA driver setup()")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Florian fainelli <f.fainelli@gmail.com>
Reported-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20210112004831.3778323-1-olteanv@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/dsa/dsa2.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -353,9 +353,13 @@ static int dsa_port_devlink_setup(struct

static void dsa_port_teardown(struct dsa_port *dp)
{
+ struct devlink_port *dlp = &dp->devlink_port;
+
if (!dp->setup)
return;

+ devlink_port_type_clear(dlp);
+
switch (dp->type) {
case DSA_PORT_TYPE_UNUSED:
break;