[PATCH 5.4 011/108] ieee802154/adf7242: defer destroy_workqueue call

Greg Kroah-Hartman
2022-09-13T14:53:10Z

From: Lin Ma <linma@zju.edu.cn>

[ Upstream commit afe7116f6d3b888778ed6d95e3cf724767b9aedf ]

There is a possible race condition (use-after-free) like below

(FREE) | (USE)
adf7242_remove | adf7242_channel
cancel_delayed_work_sync |
destroy_workqueue (1) | adf7242_cmd_rx
| mod_delayed_work (2)
|

The root cause for this race is that the upper layer (ieee802154) is
unaware of this detaching event and the function adf7242_channel can
be called without any checks.

To fix this, we can add a flag write at the beginning of adf7242_remove
and add flag check in adf7242_channel. Or we can just defer the
destructive operation like other commit 3e0588c291d6 ("hamradio: defer
ax25 kfree after unregister_netdev") which let the
ieee802154_unregister_hw() to handle the synchronization. This patch
takes the second option.

Fixes: 58e9683d1475 ("net: ieee802154: adf7242: Fix OCL calibration
runs")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Link: https://lore.kernel.org/r/20220808034224.12642-1-linma@zju.edu.cn
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ieee802154/adf7242.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ieee802154/adf7242.c b/drivers/net/ieee802154/adf7242.c
index 5945ac5f38eea..cb29da961e12b 100644
--- a/drivers/net/ieee802154/adf7242.c
+++ b/drivers/net/ieee802154/adf7242.c
@@ -1310,10 +1310,11 @@ static int adf7242_remove(struct spi_device *spi)

debugfs_remove_recursive(lp->debugfs_root);

+ ieee802154_unregister_hw(lp->hw);
+
cancel_delayed_work_sync(&lp->work);
destroy_workqueue(lp->wqueue);

- ieee802154_unregister_hw(lp->hw);
mutex_destroy(&lp->bmux);
ieee802154_free_hw(lp->hw);

--
2.35.1