[PATCH v3 7/8] clk: clocking-wizard: Fix division by zero and unbounded register write

[Shubhrajyoti Datta]

1. clk_wzrd_determine_rate(): DIV_ROUND_CLOSEST() can return 0 when
   the requested rate greatly exceeds the parent rate, causing a
   division by zero on the subsequent parent_rate / div. Clamp div
   to a minimum of 1.

2. clk_wzrd_dynamic_reconfig(): min_t() result was not assigned back
   to value, so the cap to WZRD_DR_MAX_INT_DIV_VALUE was never applied
   before the register write.

3. clk_wzrd_get_divisors() and clk_wzrd_get_divisors_ver(): If rate is
   0, DIV_ROUND_CLOSEST_ULL divides by zero. Return -EINVAL early.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xxxxxxx>
---

(no changes since v2)

Changes in v2:
Patch added

 drivers/clk/xilinx/clk-xlnx-clock-wizard.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/xilinx/clk-xlnx-clock-wizard.c b/drivers/clk/xilinx/clk-xlnx-clock-wizard.c
index 4ddcb4135306..b16656a11f4b 100644
--- a/drivers/clk/xilinx/clk-xlnx-clock-wizard.c
+++ b/drivers/clk/xilinx/clk-xlnx-clock-wizard.c
@@ -296,7 +296,7 @@ static int clk_wzrd_dynamic_reconfig(struct clk_hw *hw, unsigned long rate,
 	value = DIV_ROUND_CLOSEST(parent_rate, rate);
 
 	/* Cap the value to max */
-	min_t(u32, value, WZRD_DR_MAX_INT_DIV_VALUE);
+	value = min_t(u32, value, WZRD_DR_MAX_INT_DIV_VALUE);
 
 	/* Set divisor and clear phase offset */
 	writel(value, div_addr);
@@ -334,6 +334,8 @@ static int clk_wzrd_determine_rate(struct clk_hw *hw,
 	 * achievable
 	 */
 	div = DIV_ROUND_CLOSEST(req->best_parent_rate, req->rate);
+	if (!div)
+		div = 1;
 
 	req->rate = req->best_parent_rate / div;
 
@@ -348,6 +350,9 @@ static int clk_wzrd_get_divisors_ver(struct clk_hw *hw, unsigned long rate,
 	u32 m, d, o;
 	u32 mmin, mmax, dmin, dmax, omin, omax;
 
+	if (!rate)
+		return -EINVAL;
+
 	mmin = VER_WZRD_M_MIN;
 	mmax = VER_WZRD_M_MAX;
 	dmin = VER_WZRD_D_MIN;
@@ -390,6 +395,9 @@ static int clk_wzrd_get_divisors(struct clk_hw *hw, unsigned long rate,
 	u64 m, d, o;
 	u64 mmin, mmax, dmin, dmax, omin, omax, mdmin, mdmax;
 
+	if (!rate)
+		return -EINVAL;
+
 	mmin = WZRD_M_MIN << 3;
 	mmax = WZRD_M_MAX << 3;
 	dmin = WZRD_D_MIN;
-- 
2.34.1