Hi,
In addition to Marc’s comment, I also have security concerns.
On Fri. 22 Jan 2021 at 15:22, Su Yanjun <suyanjun218@xxxxxxxxx> wrote:
> When i debug mcp2518fd, some method to track registers is
> needed. This easy debug interface will be ok.
>
> For example,
> read a register at 0xe00:
> echo 0xe00 > can_get_reg
> cat can_get_reg
>
> write a register at 0xe00:
> echo 0xe00,0x60 > can_set_reg
What about:
printf "A%0.s" {1..1000} > can_set_reg
Doesn’t it crash the kernel?
I see no checks of the buf len in your code and I suspect it to be
vulnerable to stack buffer overflow exploits.
> Signed-off-by: Su Yanjun <suyanjun218@xxxxxxxxx>
> ---
> .../net/can/spi/mcp251xfd/mcp251xfd-core.c | 132 ++++++++++++++++++
> 1 file changed, 132 insertions(+)
>
> diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> index ab8aad0a7594..d65abe5505d5 100644
> --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> @@ -27,6 +27,131 @@
>
> #define DEVICE_NAME "mcp251xfd"
>
> +/* Add sysfs debug interface for easy to debug
> + *
> + * For example,
> + *
> + * - read a register
> + * echo 0xe00 > can_get_reg
> + * cat can_get_reg
> + *
> + * - write a register
> + * echo 0xe00,0x1 > can_set_reg
> + *
> + */
> +static int reg_offset;
> +
> +static int __get_param(const char *buf, char *off, char *val)
> +{
> + int len;
> +
> + if (!buf || !off || !val)
> + return -EINVAL;
> +
> + len = 0;
> + while (*buf != ',') {
> + *off++ = *buf++;
> + len++;
> +
> + if (len >= 16)
> + return -EINVAL;
> + }
> +
> + buf++;
> +
> + *off = '\0';
> +
> + len = 0;
> + while (*buf) {
> + *val++ = *buf++;
> + len++;
> +
> + if (len >= 16)
> + return -EINVAL;
> + }
> +
> + *val = '\0';
> +
> + return 0;
> +}
> +
> +static ssize_t can_get_reg_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int err;
> + u32 val;
> + struct mcp251xfd_priv *priv;
> +
> + priv = dev_get_drvdata(dev);
> +
> + err = regmap_read(priv->map_reg, reg_offset, &val);
> + if (err)
> + return 0;
> +
> + return sprintf(buf, "reg = 0x%08x, val = 0x%08x\n", reg_offset, val);
> +}
> +
> +static ssize_t can_get_reg_store(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t len)
> +{
> + u32 off;
> +
> + reg_offset = 0;
> +
> + if (kstrtouint(buf, 0, &off) || (off % 4))
> + return -EINVAL;
> +
> + reg_offset = off;
> +
> + return len;
> +}
> +
> +static ssize_t can_set_reg_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + return 0;
> +}
> +
> +static ssize_t can_set_reg_store(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t len)
> +{
> + struct mcp251xfd_priv *priv;
> + u32 off, val;
> + int err;
> +
> + char s1[16];
> + char s2[16];
> +
> + if (__get_param(buf, s1, s2))
> + return -EINVAL;
> +
> + if (kstrtouint(s1, 0, &off) || (off % 4))
> + return -EINVAL;
> +
> + if (kstrtouint(s2, 0, &val))
> + return -EINVAL;
> +
> + err = regmap_write(priv->map_reg, off, val);
> + if (err)
> + return -EINVAL;
> +
> + return len;
> +}
> +
> +static DEVICE_ATTR_RW(can_get_reg);
> +static DEVICE_ATTR_RW(can_set_reg);
> +
> +static struct attribute *can_attributes[] = {
> + &dev_attr_can_get_reg.attr,
> + &dev_attr_can_set_reg.attr,
> + NULL
> +};
> +
> +static const struct attribute_group can_group = {
> + .attrs = can_attributes,
> + NULL
> +};
> +
> static const struct mcp251xfd_devtype_data mcp251xfd_devtype_data_mcp2517fd = {
> .quirks = MCP251XFD_QUIRK_MAB_NO_WARN | MCP251XFD_QUIRK_CRC_REG |
> MCP251XFD_QUIRK_CRC_RX | MCP251XFD_QUIRK_CRC_TX |
> @@ -2944,6 +3069,12 @@ static int mcp251xfd_probe(struct spi_device *spi)
> if (err)
> goto out_free_candev;
>
> + err = sysfs_create_group(&spi->dev.kobj, &can_group);
> + if (err) {
> + netdev_err(priv->ndev, "Create can group fail.\n");
> + goto out_free_candev;
> + }
> +
> err = can_rx_offload_add_manual(ndev, &priv->offload,
> MCP251XFD_NAPI_WEIGHT);
> if (err)
> @@ -2972,6 +3103,7 @@ static int mcp251xfd_remove(struct spi_device *spi)
> mcp251xfd_unregister(priv);
> spi->max_speed_hz = priv->spi_max_speed_hz_orig;
> free_candev(ndev);
> + sysfs_remove_group(&spi->dev.kobj, &can_group);
>
> return 0;
> }
> --
> 2.25.1
>
