linux-kernel - [PATCH 1/3] clk: bcm: rpi: Prevent out-of-bounds access

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Message-Id: <20220713154953.3336-2-stefan.wahren@i2se.com>
Date:   Wed, 13 Jul 2022 17:49:51 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     bcm-kernel-feedback-list@...adcom.com,
        Maxime Ripard <maxime@...no.tech>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Stefan Wahren <stefan.wahren@...e.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: [PATCH 1/3] clk: bcm: rpi: Prevent out-of-bounds access

The while loop in raspberrypi_discover_clocks() relies on the assumption
that the id of the last clock element is zero. Because this data comes
from the Videocore firmware and it doesn't guarantuee such a behavior
this could lead to out-of-bounds access. So fix this by providing
a sentinel element.

Fixes: 93d2725affd6 ("clk: bcm: rpi: Discover the firmware clocks")
Link: https://github.com/raspberrypi/firmware/issues/1688
Suggested-by: Phil Elwell <phil@...pberrypi.com>
Signed-off-by: Stefan Wahren <stefan.wahren@...e.com>
---
 drivers/clk/bcm/clk-raspberrypi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/bcm/clk-raspberrypi.c b/drivers/clk/bcm/clk-raspberrypi.c
index 73518009a0f2..79cbf0c0b401 100644
--- a/drivers/clk/bcm/clk-raspberrypi.c
+++ b/drivers/clk/bcm/clk-raspberrypi.c
@@ -344,8 +344,13 @@ static int raspberrypi_discover_clocks(struct raspberrypi_clk *rpi,
 	struct rpi_firmware_get_clocks_response *clks;
 	int ret;
 
+	/*
+	 * The firmware doesn't guarantee that the last element of
+	 * RPI_FIRMWARE_GET_CLOCKS is zeroed. So allocate an additional
+	 * zero element as sentinel.
+	 */
 	clks = devm_kcalloc(rpi->dev,
-			    RPI_FIRMWARE_NUM_CLK_ID, sizeof(*clks),
+			    RPI_FIRMWARE_NUM_CLK_ID + 1, sizeof(*clks),
 			    GFP_KERNEL);
 	if (!clks)
 		return -ENOMEM;
-- 
2.25.1