linux-kernel - Re: [PATCH 6/6] platform/chrome: cros_ec_spi: drop BUG

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Date:   Thu, 12 May 2022 08:14:10 -0700
From:   Guenter Roeck <groeck@...gle.com>
To:     Tzung-Bi Shih <tzungbi@...nel.org>
Cc:     Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        chrome-platform@...ts.linux.dev,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/6] platform/chrome: cros_ec_spi: drop BUG_ON()

On Thu, May 12, 2022 at 1:37 AM Tzung-Bi Shih <tzungbi@...nel.org> wrote:
>
> It is overkill to crash the kernel if the `din` buffer is going to full
> or overflow.
>
> Drop the BUG_ON() and return -EINVAL instead.
>
> Signed-off-by: Tzung-Bi Shih <tzungbi@...nel.org>

Wonder if the return code should be -EPROTO instead, but I don't have
a strong opinion.

Reviewed-by: Guenter Roeck <groeck@...omium.org>

> ---
>  drivers/platform/chrome/cros_ec_spi.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/platform/chrome/cros_ec_spi.c b/drivers/platform/chrome/cros_ec_spi.c
> index 589f18e9537d..0a938f317adc 100644
> --- a/drivers/platform/chrome/cros_ec_spi.c
> +++ b/drivers/platform/chrome/cros_ec_spi.c
> @@ -160,7 +160,8 @@ static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n)
>         struct spi_message msg;
>         int ret;
>
> -       BUG_ON(buf - ec_dev->din + n > ec_dev->din_size);
> +       if (buf - ec_dev->din + n > ec_dev->din_size)
> +               return -EINVAL;
>
>         memset(&trans, 0, sizeof(trans));
>         trans.cs_change = 1;
> @@ -197,7 +198,8 @@ static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
>         unsigned long deadline;
>         int todo;
>
> -       BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
> +       if (ec_dev->din_size < EC_MSG_PREAMBLE_COUNT)
> +               return -EINVAL;
>
>         /* Receive data until we see the header byte */
>         deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
> @@ -237,7 +239,8 @@ static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
>          * start of our buffer
>          */
>         todo = end - ++ptr;
> -       BUG_ON(todo < 0 || todo > ec_dev->din_size);
> +       if (todo < 0 || todo > ec_dev->din_size)
> +               return -EINVAL;
>         todo = min(todo, need_len);
>         memmove(ec_dev->din, ptr, todo);
>         ptr = ec_dev->din + todo;
> @@ -305,7 +308,8 @@ static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
>         unsigned long deadline;
>         int todo;
>
> -       BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
> +       if (ec_dev->din_size < EC_MSG_PREAMBLE_COUNT)
> +               return -EINVAL;
>
>         /* Receive data until we see the header byte */
>         deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
> @@ -345,7 +349,8 @@ static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
>          * start of our buffer
>          */
>         todo = end - ++ptr;
> -       BUG_ON(todo < 0 || todo > ec_dev->din_size);
> +       if (todo < 0 || todo > ec_dev->din_size)
> +               return -EINVAL;
>         todo = min(todo, need_len);
>         memmove(ec_dev->din, ptr, todo);
>         ptr = ec_dev->din + todo;
> --
> 2.36.0.512.ge40c2bad7a-goog
>