netdev - [PATCH net-next] net: phylink: don't call netif_carrier

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Date:   Fri, 17 Sep 2021 14:36:31 +0100
From:   "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        Joakim Zhang <qiangqing.zhang@....com>
Subject: [PATCH net-next] net: phylink: don't call netif_carrier_off() with
 NULL netdev

Dan Carpenter points out that we have a code path that permits a NULL
netdev pointer to be passed to netif_carrier_off(), which will cause
a kernel oops. In any case, we need to set pl->old_link_state to false
to have the desired effect when there is no netdev present.

Fixes: f97493657c63 ("net: phylink: add suspend/resume support")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
This does not need to be queued for -rc as there is only one user of
phylink_suspend(), which will always have a non-NULL netdev pointer.
Hence, submitting for net-next is appropriate.

 drivers/net/phy/phylink.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 0a0abe8e4be0..5a58c77d0002 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1333,7 +1333,10 @@ void phylink_suspend(struct phylink *pl, bool mac_wol)
 		 * but one would hope all packets have been sent. This
 		 * also means phylink_resolve() will do nothing.
 		 */
-		netif_carrier_off(pl->netdev);
+		if (pl->netdev)
+			netif_carrier_off(pl->netdev);
+		else
+			pl->old_link_state = false;
 
 		/* We do not call mac_link_down() here as we want the
 		 * link to remain up to receive the WoL packets.
-- 
2.30.2