linux-kernel - [PATCH] usb: typec: tps6598x: Remove VLA usage

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Message-ID: <20180620182840.GA24775@beast>
Date:   Wed, 20 Jun 2018 11:28:40 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: [PATCH] usb: typec: tps6598x: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
uses the maximum buffer size and adds a sanity check.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/usb/typec/tps6598x.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/typec/tps6598x.c b/drivers/usb/typec/tps6598x.c
index 4b4c8d271b27..396193f85e6d 100644
--- a/drivers/usb/typec/tps6598x.c
+++ b/drivers/usb/typec/tps6598x.c
@@ -81,12 +81,17 @@ struct tps6598x {
 	struct typec_capability typec_cap;
 };
 
+#define TPS_MAX_LEN	sizeof(u64)
+
 static int
 tps6598x_block_read(struct tps6598x *tps, u8 reg, void *val, size_t len)
 {
-	u8 data[len + 1];
+	u8 data[TPS_MAX_LEN + 1];
 	int ret;
 
+	if (WARN_ON(len + 1 > sizeof(data)))
+		return -EINVAL;
+
 	if (!tps->i2c_protocol)
 		return regmap_raw_read(tps->regmap, reg, val, len);
 
-- 
2.17.1


-- 
Kees Cook
Pixel Security