[PATCH 6.1 0934/1146] mctp: Remove device type check at unregister

Greg Kroah-Hartman
2022-12-28T16:49:15Z

From: Matt Johnston <matt@codeconstruct.com.au>

[ Upstream commit b389a902dd5be4ece505a2e0463b9b034de04bf5 ]

The unregister check could be incorrectly triggered if a netdev
changes its type after register. That is possible for a tun device
using TUNSETLINK ioctl, resulting in mctp unregister failing
and the netdev unregister waiting forever.

This was encountered by https://github.com/openthread/openthread/issues/8523

Neither check at register or unregister is required. They were added in
an attempt to track down mctp_ptr being set unexpectedly, which should
not happen in normal operation.

Fixes: 7b1871af75f3 ("mctp: Warn if pointer is set for a wrong dev type")
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Link: https://lore.kernel.org/r/20221215054933.2403401-1-matt@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/mctp/device.c | 14 +-------------
1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/net/mctp/device.c b/net/mctp/device.c
index 99a3bda8852f..acb97b257428 100644
--- a/net/mctp/device.c
+++ b/net/mctp/device.c
@@ -429,12 +429,6 @@ static void mctp_unregister(struct net_device *dev)
struct mctp_dev *mdev;

mdev = mctp_dev_get_rtnl(dev);
- if (mdev && !mctp_known(dev)) {
- // Sanity check, should match what was set in mctp_register
- netdev_warn(dev, "%s: BUG mctp_ptr set for unknown type %d",
- __func__, dev->type);
- return;
- }
if (!mdev)
return;

@@ -451,14 +445,8 @@ static int mctp_register(struct net_device *dev)
struct mctp_dev *mdev;

/* Already registered? */
- mdev = rtnl_dereference(dev->mctp_ptr);
-
- if (mdev) {
- if (!mctp_known(dev))
- netdev_warn(dev, "%s: BUG mctp_ptr set for unknown type %d",
- __func__, dev->type);
+ if (rtnl_dereference(dev->mctp_ptr))
return 0;
- }

/* only register specific types */
if (!mctp_known(dev))
--
2.35.1