[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 <redacted>
Signed-off-by: Russell King (Oracle) <redacted>
---
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

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Fri, 17 Sep 2021 14:36:31 +0100 you wrote:

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 <redacted>
Signed-off-by: Russell King (Oracle) <redacted>

[...]

Here is the summary with links:
  - [net-next] net: phylink: don't call netif_carrier_off() with NULL netdev
    https://git.kernel.org/netdev/net-next/c/cbcca2e3961e

You are awesome, thank you!
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