[PATCH net v1] net: ravb: fix use-after-free in ravb_get_ts_info

[xuanqiang.luo@linux.dev]

From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>

The PHC is registered by ravb_open() and unregistered by ravb_close().
However, ravb_ptp_stop() leaves priv->ptp.clock pointing at the freed
clock. Since the netdev remains registered after ndo_stop, get_ts_info
can still pass the dangling pointer to ptp_clock_index(), resulting in a
use-after-free.

Clear the pointer after unregistering the clock and only query the index
while a clock is registered.

Fixes: a0d2f20650e8 ("Renesas Ethernet AVB PTP clock driver")
Cc: stable@vger.kernel.org
Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
---
I don't have access to RAVB hardware to reproduce the issue. To aid
review, see the similar PHC lifetime fix merged as commit 8da13e6d63c1
("net: macb: fix use-after-free access to PTP clock").

 drivers/net/ethernet/renesas/ravb_main.c | 3 ++-
 drivers/net/ethernet/renesas/ravb_ptp.c  | 5 ++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 5f88733094d0f..3a9d9f8718216 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1779,7 +1779,8 @@ static int ravb_get_ts_info(struct net_device *ndev,
 			(1 << HWTSTAMP_FILTER_NONE) |
 			(1 << HWTSTAMP_FILTER_PTP_V2_L2_EVENT) |
 			(1 << HWTSTAMP_FILTER_ALL);
-		info->phc_index = ptp_clock_index(priv->ptp.clock);
+		if (priv->ptp.clock)
+			info->phc_index = ptp_clock_index(priv->ptp.clock);
 	}
 
 	return 0;
diff --git a/drivers/net/ethernet/renesas/ravb_ptp.c b/drivers/net/ethernet/renesas/ravb_ptp.c
index 226c6c0ab945b..fc8c601ed3a5e 100644
--- a/drivers/net/ethernet/renesas/ravb_ptp.c
+++ b/drivers/net/ethernet/renesas/ravb_ptp.c
@@ -337,5 +337,8 @@ void ravb_ptp_stop(struct net_device *ndev)
 	ravb_write(ndev, 0, GIC);
 	ravb_write(ndev, 0, GIS);
 
-	ptp_clock_unregister(priv->ptp.clock);
+	if (priv->ptp.clock) {
+		ptp_clock_unregister(priv->ptp.clock);
+		priv->ptp.clock = NULL;
+	}
 }
-- 
2.43.0