netdev - [PATCH AUTOSEL 4.19 05/10] net: ethernet: ravb: exit if re-initialization fails in tx timeout

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Message-Id: <20200727232443.718000-5-sashal@kernel.org>
Date:   Mon, 27 Jul 2020 19:24:38 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Dirk Behme <dirk.behme@...bosch.com>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 05/10] net: ethernet: ravb: exit if re-initialization fails in tx timeout

From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>

[ Upstream commit 015c5d5e6aa3523c758a70eb87b291cece2dbbb4 ]

According to the report of [1], this driver is possible to cause
the following error in ravb_tx_timeout_work().

ravb e6800000.ethernet ethernet: failed to switch device to config mode

This error means that the hardware could not change the state
from "Operation" to "Configuration" while some tx and/or rx queue
are operating. After that, ravb_config() in ravb_dmac_init() will fail,
and then any descriptors will be not allocaled anymore so that NULL
pointer dereference happens after that on ravb_start_xmit().

To fix the issue, the ravb_tx_timeout_work() should check
the return values of ravb_stop_dma() and ravb_dmac_init().
If ravb_stop_dma() fails, ravb_tx_timeout_work() re-enables TX and RX
and just exits. If ravb_dmac_init() fails, just exits.

[1]
https://lore.kernel.org/linux-renesas-soc/20200518045452.2390-1-dirk.behme@de.bosch.com/

Reported-by: Dirk Behme <dirk.behme@...bosch.com>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Reviewed-by: Sergei Shtylyov <sergei.shtylyov@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/renesas/ravb_main.c | 26 ++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index faaf74073a120..569e698b5c807 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1445,6 +1445,7 @@ static void ravb_tx_timeout_work(struct work_struct *work)
 	struct ravb_private *priv = container_of(work, struct ravb_private,
 						 work);
 	struct net_device *ndev = priv->ndev;
+	int error;
 
 	netif_tx_stop_all_queues(ndev);
 
@@ -1453,15 +1454,36 @@ static void ravb_tx_timeout_work(struct work_struct *work)
 		ravb_ptp_stop(ndev);
 
 	/* Wait for DMA stopping */
-	ravb_stop_dma(ndev);
+	if (ravb_stop_dma(ndev)) {
+		/* If ravb_stop_dma() fails, the hardware is still operating
+		 * for TX and/or RX. So, this should not call the following
+		 * functions because ravb_dmac_init() is possible to fail too.
+		 * Also, this should not retry ravb_stop_dma() again and again
+		 * here because it's possible to wait forever. So, this just
+		 * re-enables the TX and RX and skip the following
+		 * re-initialization procedure.
+		 */
+		ravb_rcv_snd_enable(ndev);
+		goto out;
+	}
 
 	ravb_ring_free(ndev, RAVB_BE);
 	ravb_ring_free(ndev, RAVB_NC);
 
 	/* Device init */
-	ravb_dmac_init(ndev);
+	error = ravb_dmac_init(ndev);
+	if (error) {
+		/* If ravb_dmac_init() fails, descriptors are freed. So, this
+		 * should return here to avoid re-enabling the TX and RX in
+		 * ravb_emac_init().
+		 */
+		netdev_err(ndev, "%s: ravb_dmac_init() failed, error %d\n",
+			   __func__, error);
+		return;
+	}
 	ravb_emac_init(ndev);
 
+out:
 	/* Initialise PTP Clock driver */
 	if (priv->chip_id == RCAR_GEN2)
 		ravb_ptp_init(ndev, priv->pdev);
-- 
2.25.1