linux-kernel - [PATCH] mtd: nand: sunxi: fix potential divide-by-zero error

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Message-Id: <1501248177-575-1-git-send-email-pure.logic@nexus-software.ie>
Date:   Fri, 28 Jul 2017 14:22:57 +0100
From:   Bryan O'Donoghue <pure.logic@...us-software.ie>
To:     boris.brezillon@...e-electrons.com
Cc:     richard@....at, dwmw2@...radead.org, computersforpeace@...il.com,
        marek.vasut@...il.com, cyrille.pitchen@...ev4u.fr,
        maxime.ripard@...e-electrons.com, wens@...e.org,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Bryan O'Donoghue <pure.logic@...us-software.ie>
Subject: [PATCH] mtd: nand: sunxi: fix potential divide-by-zero error

clk_round_rate() can return <= 0. Currently the value returned by
clk_round_rate() is used directly for a division. This patch introduces a
guard to ensure a divide-by-zero or a divide by a negative number for that
matter can't happen by bugging out returning -EINVAL if clk_round_rate()
returns <= 0.

Fixes: 2d43457f79e4 ("mtd: nand: sunxi: fix EDO mode selection")

Signed-off-by: Bryan O'Donoghue <pure.logic@...us-software.ie>
---
 drivers/mtd/nand/sunxi_nand.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
index d0b6f8f..6abd142 100644
--- a/drivers/mtd/nand/sunxi_nand.c
+++ b/drivers/mtd/nand/sunxi_nand.c
@@ -1728,6 +1728,10 @@ static int sunxi_nfc_setup_data_interface(struct mtd_info *mtd, int csline,
 	 */
 	chip->clk_rate = NSEC_PER_SEC / min_clk_period;
 	real_clk_rate = clk_round_rate(nfc->mod_clk, chip->clk_rate);
+	if (real_clk_rate <= 0) {
+		dev_err(nfc->dev, "Unable to round clk %lu\n", chip->clk_rate);
+		return -EINVAL;
+	}
 
 	/*
 	 * ONFI specification 3.1, paragraph 4.15.2 dictates that EDO data
-- 
2.7.4