alx: acquire mutex for alx_reinit in alx_change_mtu

alx_reinit has a lockdep assertion that the alx->mtx mutex must be held.
alx_reinit is called from two places: alx_reset and alx_change_mtu.
alx_reset does acquire alx->mtx before calling alx_reinit.
alx_change_mtu does not acquire this mutex, nor do its callers or any
path towards alx_change_mtu.
Acquire the mutex in alx_change_mtu.

The issue was introduced when the fine-grained locking was introduced
to the code to replace the RTNL. The same commit also introduced the
lockdep assertion.

Fixes: 4a5fe57e7751 ("alx: use fine-grained locking instead of RTNL")
Signed-off-by: Niels Dossche <dossche.niels@gmail.com>
Link: https://lore.kernel.org/r/20220310232707.44251-1-dossche.niels@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/atheros/alx/main.c b/drivers/net/ethernet/atheros/alx/main.c
index 4ad3fc72e74e323f65a333bd2baad0e815ea34b0..a89b93cb4e26d91c8ab1be848b4a06696b30946b 100644 (file)
--- a/drivers/net/ethernet/atheros/alx/main.c
+++ b/drivers/net/ethernet/atheros/alx/main.c
@@ -1181,8 +1181,11 @@ static int alx_change_mtu(struct net_device *netdev, int mtu)
        alx->hw.mtu = mtu;
        alx->rxbuf_size = max(max_frame, ALX_DEF_RXBUF_SIZE);
        netdev_update_features(netdev);
-       if (netif_running(netdev))
+       if (netif_running(netdev)) {
+               mutex_lock(&alx->mtx);
                alx_reinit(alx);
+               mutex_unlock(&alx->mtx);
+       }
        return 0;
 }