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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Lin Ma <linma@zju.edu.cn>,
        Michael Hennerich <michael.hennerich@analog.com>,
        Stefan Schmidt <stefan@datenfreihafen.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 011/108] ieee802154/adf7242: defer destroy_workqueue call
Date:   Tue, 13 Sep 2022 16:05:42 +0200
Message-Id: <20220913140354.042864730@linuxfoundation.org>
In-Reply-To: <20220913140353.549108748@linuxfoundation.org>
References: <20220913140353.549108748@linuxfoundation.org>
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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