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Message-ID: <CAGXu5jK-qTdkDi2bC7DZg-bR-tFjSGOZsNB9_b-F++qMgdcF+Q@mail.gmail.com>
Date: Fri, 18 May 2018 11:01:55 -0700
From: Kees Cook <keescook@...omium.org>
To: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Laura Abbott <labbott@...hat.com>, Russell King <linux@...linux.org.uk>,
David Airlie <airlied@...ux.ie>,
Maling list - DRI developers <dri-devel@...ts.freedesktop.org>, LKML <linux-kernel@...r.kernel.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCHv2] drm/i2c: tda998x: Remove VLA usage
On Tue, Apr 10, 2018 at 6:03 PM, Laura Abbott <labbott@...hat.com> wrote:
> There's an ongoing effort to remove VLAs[1] from the kernel to eventually
> turn on -Wvla. The vla in reg_write_range is based on the length of data
> passed. The one use of a non-constant size for this range is bounded by
> the size buffer passed to hdmi_infoframe_pack which is a fixed size.
> Switch to this upper bound.
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Same question for this patch: who's best to take this?
Thanks!
-Kees
> ---
> v2: Switch to make the buffer size more transparent and add a bounds
> check.
> ---
> drivers/gpu/drm/i2c/tda998x_drv.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
> index 9e67a7b4e3a4..c8b6029b7839 100644
> --- a/drivers/gpu/drm/i2c/tda998x_drv.c
> +++ b/drivers/gpu/drm/i2c/tda998x_drv.c
> @@ -466,13 +466,22 @@ reg_read_range(struct tda998x_priv *priv, u16 reg, char *buf, int cnt)
> return ret;
> }
>
> +#define MAX_WRITE_RANGE_BUF 32
> +
> static void
> reg_write_range(struct tda998x_priv *priv, u16 reg, u8 *p, int cnt)
> {
> struct i2c_client *client = priv->hdmi;
> - u8 buf[cnt+1];
> + /* This is the maximum size of the buffer passed in */
> + u8 buf[MAX_WRITE_RANGE_BUF + 1];
> int ret;
>
> + if (cnt > MAX_WRITE_RANGE_BUF) {
> + dev_err(&client->dev, "Fixed write buffer too small (%d)\n",
> + MAX_WRITE_RANGE_BUF);
> + return;
> + }
> +
> buf[0] = REG2ADDR(reg);
> memcpy(&buf[1], p, cnt);
>
> @@ -679,7 +688,7 @@ static void
> tda998x_write_if(struct tda998x_priv *priv, u8 bit, u16 addr,
> union hdmi_infoframe *frame)
> {
> - u8 buf[32];
> + u8 buf[MAX_WRITE_RANGE_BUF];
> ssize_t len;
>
> len = hdmi_infoframe_pack(frame, buf, sizeof(buf));
> --
> 2.14.3
>
--
Kees Cook
Pixel Security
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