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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Vladimir Oltean <vladimir.oltean@nxp.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.12 493/700] net: dsa: sja1105: fix NULL pointer dereference in sja1105_reload_cbs()
Date:   Mon, 12 Jul 2021 08:09:36 +0200
Message-Id: <20210712061028.979830367@linuxfoundation.org>
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From: Vladimir Oltean <vladimir.oltean@nxp.com>

[ Upstream commit be7f62eebaff2f86c1467a2d33930a0a7a87675b ]

priv->cbs is an array of priv->info->num_cbs_shapers elements of type
struct sja1105_cbs_entry which only get allocated if CONFIG_NET_SCH_CBS
is enabled.

However, sja1105_reload_cbs() is called from sja1105_static_config_reload()
which in turn is called for any of the items in sja1105_reset_reasons,
therefore during the normal runtime of the driver and not just from a
code path which can be triggered by the tc-cbs offload.

The sja1105_reload_cbs() function does not contain a check whether the
priv->cbs array is NULL or not, it just assumes it isn't and proceeds to
iterate through the credit-based shaper elements. This leads to a NULL
pointer dereference.

The solution is to return success if the priv->cbs array has not been
allocated, since sja1105_reload_cbs() has nothing to do.

Fixes: 4d7525085a9b ("net: dsa: sja1105: offload the Credit-Based Shaper qdisc")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/dsa/sja1105/sja1105_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index 926544440f02..42a0fb588f64 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -1798,6 +1798,12 @@ static int sja1105_reload_cbs(struct sja1105_private *priv)
 {
 	int rc = 0, i;
 
+	/* The credit based shapers are only allocated if
+	 * CONFIG_NET_SCH_CBS is enabled.
+	 */
+	if (!priv->cbs)
+		return 0;
+
 	for (i = 0; i < priv->info->num_cbs_shapers; i++) {
 		struct sja1105_cbs_entry *cbs = &priv->cbs[i];
 
-- 
2.30.2