linux-kernel - [PATCH] drm/i2c: tda9950: Remove VLA usage

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Date:   Wed, 20 Jun 2018 11:27:23 -0700
From:   Kees Cook <keescook@...omium.org>
To:     David Airlie <airlied@...ux.ie>
Cc:     linux-kernel@...r.kernel.org,
        Hans Verkuil <hans.verkuil@...co.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH] drm/i2c: tda9950: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
sets the buffer to maximum 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/gpu/drm/i2c/tda9950.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i2c/tda9950.c b/drivers/gpu/drm/i2c/tda9950.c
index 3f7396caad48..28314433c351 100644
--- a/drivers/gpu/drm/i2c/tda9950.c
+++ b/drivers/gpu/drm/i2c/tda9950.c
@@ -76,9 +76,12 @@ struct tda9950_priv {
 static int tda9950_write_range(struct i2c_client *client, u8 addr, u8 *p, int cnt)
 {
 	struct i2c_msg msg;
-	u8 buf[cnt + 1];
+	u8 buf[CEC_MAX_MSG_SIZE + 3];
 	int ret;
 
+	if (WARN_ON(cnt > sizeof(buf)))
+		return -EINVAL;
+
 	buf[0] = addr;
 	memcpy(buf + 1, p, cnt);
 
-- 
2.17.1


-- 
Kees Cook
Pixel Security