linux-kernel - [PATCH RFC] renesas: add zero check for prate variable

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Message-ID: <20250327151109.9648-1-tsogomonian@astralinux.ru>
Date: Thu, 27 Mar 2025 18:10:44 +0300
From: Tigran Sogomonian <tsogomonian@...ralinux.ru>
To: Geert Uytterhoeven <geert+renesas@...der.be>
Cc: Tigran Sogomonian <tsogomonian@...ralinux.ru>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	linux-renesas-soc@...r.kernel.org,
	linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org
Subject: [PATCH RFC] renesas: add zero check for prate variable

To avoid division by zero, a check was added to the prate
variable, since no guarantees were found that it could not
be equal to zero.

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

Signed-off-by: Tigran Sogomonian <tsogomonian@...ralinux.ru>
---
 drivers/clk/renesas/rcar-gen3-cpg.c | 2 ++
 drivers/clk/renesas/rcar-gen4-cpg.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/drivers/clk/renesas/rcar-gen3-cpg.c b/drivers/clk/renesas/rcar-gen3-cpg.c
index 027100e84ee4..66da3b4398cd 100644
--- a/drivers/clk/renesas/rcar-gen3-cpg.c
+++ b/drivers/clk/renesas/rcar-gen3-cpg.c
@@ -205,6 +205,8 @@ static int cpg_z_clk_determine_rate(struct clk_hw *hw,
 						  prate * zclk->fixed_div);
 
 	prate = req->best_parent_rate / zclk->fixed_div;
+	if (prate == 0)
+		return -EINVAL;
 	min_mult = max(div64_ul(req->min_rate * 32ULL, prate), 1ULL);
 	max_mult = min(div64_ul(req->max_rate * 32ULL, prate), 32ULL);
 	if (max_mult < min_mult)
diff --git a/drivers/clk/renesas/rcar-gen4-cpg.c b/drivers/clk/renesas/rcar-gen4-cpg.c
index 31aa790fd003..4c9a7d699290 100644
--- a/drivers/clk/renesas/rcar-gen4-cpg.c
+++ b/drivers/clk/renesas/rcar-gen4-cpg.c
@@ -308,6 +308,8 @@ static int cpg_z_clk_determine_rate(struct clk_hw *hw,
 						  prate * zclk->fixed_div);
 
 	prate = req->best_parent_rate / zclk->fixed_div;
+	if (prate == 0)
+		return -EINVAL;
 	min_mult = max(div64_ul(req->min_rate * 32ULL, prate), 1ULL);
 	max_mult = min(div64_ul(req->max_rate * 32ULL, prate), 32ULL);
 	if (max_mult < min_mult)
-- 
2.47.1