[PATCH 5.10 408/593] net: dsa: sja1105: fix NULL pointer dereference in sja1105_reload_cbs()

From: Greg Kroah-Hartman
Date: Mon Jul 12 2021 - 03:08:48 EST

From: Vladimir Oltean <vladimir.oltean@xxxxxxx>

[ 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@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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 e273b2bd82ba..82852c57cc0e 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -1711,6 +1711,12 @@ 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];