[PATCH v11 1/2] clk: validate spread spectrum configuration

[Dario Binacchi <dario.binacchi@amarulasolutions.com>]

The spread spectrum configuration is passed to the provider's
set_spread_spectrum() callback without any validation, as clk-conf.c
only skips all-zero triplets from "assigned-clock-sscs". An invalid
device tree can hand providers a zero modulation frequency or a spread
ratio above 100%, and each provider would have to add the same checks
to protect e.g. divisions in its rate computations.

Fixes: c86814e70390 ("clk: Introduce clk_hw_set_spread_spectrum")
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
---

(no changes since v1)

 drivers/clk/clk.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index fef87167a60b..208caf60eeb5 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -2851,6 +2851,20 @@ int clk_hw_set_spread_spectrum(struct clk_hw *hw, const struct clk_spread_spectr
 	if (!hw)
 		return 0;
 
+	switch (ss_conf->method) {
+	case CLK_SPREAD_NO:
+		break;
+	case CLK_SPREAD_CENTER:
+	case CLK_SPREAD_UP:
+	case CLK_SPREAD_DOWN:
+		if (!ss_conf->modfreq_hz || !ss_conf->spread_bp ||
+		    ss_conf->spread_bp > 10000)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
 	core = hw->core;
 
 	clk_prepare_lock();
-- 
2.43.0