[PATCH] net: dsa: sja1105: fix division by zero in sja1105_tas_set_runtime_params()

[<Alexander.Chesnokov@kaspersky.com>]

From: Alexander Chesnokov <Alexander.Chesnokov@kaspersky.com>

If taprio offload is configured such that none of the ports' base_time
is less than S64_MAX (the initial value of earliest_base_time), then
its_cycle_time remains zero and is passed to future_base_time() as
cycle_time, causing division by zero in div_s64().

Add a check for its_cycle_time being zero before calling
future_base_time() and return -EINVAL.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 86db36a347b4 ("net: dsa: sja1105: Implement state machine for TAS with PTP clock source")
Cc: stable@vger.kernel.org

Signed-off-by: Alexander Chesnokov <Alexander.Chesnokov@kaspersky.com>
---
 drivers/net/dsa/sja1105/sja1105_tas.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/dsa/sja1105/sja1105_tas.c b/drivers/net/dsa/sja1105/sja1105_tas.c
index e6153848a950..ce4b544a2b9c 100644
--- a/drivers/net/dsa/sja1105/sja1105_tas.c
+++ b/drivers/net/dsa/sja1105/sja1105_tas.c
@@ -62,6 +62,9 @@ static int sja1105_tas_set_runtime_params(struct sja1105_private *priv)
 	if (!tas_data->enabled)
 		return 0;
 
+	if (!its_cycle_time)
+		return -EINVAL;
+
 	/* Roll the earliest base time over until it is in a comparable
 	 * time base with the latest, then compare their deltas.
 	 * We want to enforce that all ports' base times are within
-- 
2.43.0