linux-kernel - Re: [PATCH] drm/bridge: it6505: Fix the read buffer array bound

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Message-ID: <CAG3jFysyV8QHO4zEdUYLxt9eBnGsHWrXdWbicmufUPnTB-oRLA@mail.gmail.com>
Date:   Mon, 28 Feb 2022 16:13:24 +0100
From:   Robert Foss <robert.foss@...aro.org>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
Cc:     David Airlie <airlied@...ux.ie>,
        Allen Chen <allen.chen@....com.tw>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Hermes Wu <Hermes.Wu@....com.tw>,
        Daniel Vetter <daniel@...ll.ch>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] drm/bridge: it6505: Fix the read buffer array bound

On Mon, 28 Feb 2022 at 09:14, Hsin-Yi Wang <hsinyi@...omium.org> wrote:
>
> The size of read_buf is READ_BUFFER_SIZE (200), so we can't access it
> with read_buf + PAGE_SIZE (4096). Extend the READ_BUFFER_SIZE to 400 and
> set the end position to read_buf + READ_BUFFER_SIZE.
>
> Fixes: b5c84a9edcd418 ("drm/bridge: add it6505 driver")
> Reported-by: Mark Brown <broonie@...nel.org>
> Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> ---
>  drivers/gpu/drm/bridge/ite-it6505.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
> index fb16a176822d81..f2f101220ade94 100644
> --- a/drivers/gpu/drm/bridge/ite-it6505.c
> +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> @@ -289,7 +289,7 @@
>  #define WORD_LENGTH_20BIT 2
>  #define WORD_LENGTH_24BIT 3
>  #define DEBUGFS_DIR_NAME "it6505-debugfs"
> -#define READ_BUFFER_SIZE 200
> +#define READ_BUFFER_SIZE 400
>
>  /* Vendor option */
>  #define HDCP_DESIRED 1
> @@ -3074,7 +3074,7 @@ static ssize_t receive_timing_debugfs_show(struct file *file, char __user *buf,
>         struct it6505 *it6505 = file->private_data;
>         struct drm_display_mode *vid = &it6505->video_info;
>         u8 read_buf[READ_BUFFER_SIZE];
> -       u8 *str = read_buf, *end = read_buf + PAGE_SIZE;
> +       u8 *str = read_buf, *end = read_buf + READ_BUFFER_SIZE;
>         ssize_t ret, count;
>
>         if (!it6505)
> --
> 2.35.1.574.g5d30c73bfb-goog
>

Reviewed-by: Robert Foss <robert.foss@...aro.org>