linux-kernel - Re: [PATCH v1 07/10] Input: atmel_mxt_ts - zero terminate config firmware file

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Date:   Mon, 23 Jul 2018 15:35:34 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Nick Dyer <nick@...anahar.org>
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        Chris Healy <cphealy@...il.com>,
        Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Nick Dyer <nick.dyer@...ev.co.uk>
Subject: Re: [PATCH v1 07/10] Input: atmel_mxt_ts - zero terminate config
 firmware file

On Fri, Jul 20, 2018 at 10:51:19PM +0100, Nick Dyer wrote:
> From: Nick Dyer <nick.dyer@...ev.co.uk>
> 
> We use sscanf to parse the configuration file, so it's necessary to zero
> terminate the configuration otherwise a truncated file can cause the
> parser to run off into uninitialised memory.
> 
> Signed-off-by: Nick Dyer <nick.dyer@...ev.co.uk>
> ---
>  drivers/input/touchscreen/atmel_mxt_ts.c | 36 +++++++++++++++++-------
>  1 file changed, 26 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> index 0ce126e918f1..2d1fddafb7f9 100644
> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> @@ -279,7 +279,7 @@ enum mxt_suspend_mode {
>  
>  /* Config update context */
>  struct mxt_cfg {
> -	const u8 *raw;
> +	u8 *raw;
>  	size_t raw_size;
>  	off_t raw_pos;
>  
> @@ -1451,14 +1451,21 @@ static int mxt_update_cfg(struct mxt_data *data, const struct firmware *fw)
>  	u32 info_crc, config_crc, calculated_crc;
>  	u16 crc_start = 0;
>  
> -	cfg.raw = fw->data;
> +	/* Make zero terminated copy of the OBP_RAW file */
> +	cfg.raw = kzalloc(fw->size + 1, GFP_KERNEL);

kmemdup_nul()? I guess config it not that big to be concerned with
kmalloc() vs vmalloc() and allocation failures...

> +	if (!cfg.raw)
> +		return -ENOMEM;
> +
> +	memcpy(cfg.raw, fw->data, fw->size);
> +	cfg.raw[fw->size] = '\0';
>  	cfg.raw_size = fw->size;
>  
>  	mxt_update_crc(data, MXT_COMMAND_REPORTALL, 1);
>  
>  	if (strncmp(cfg.raw, MXT_CFG_MAGIC, strlen(MXT_CFG_MAGIC))) {
>  		dev_err(dev, "Unrecognised config file\n");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto release_raw;
>  	}
>  
>  	cfg.raw_pos = strlen(MXT_CFG_MAGIC);
> @@ -1470,7 +1477,8 @@ static int mxt_update_cfg(struct mxt_data *data, const struct firmware *fw)
>  			     &offset);
>  		if (ret != 1) {
>  			dev_err(dev, "Bad format\n");
> -			return -EINVAL;
> +			ret = -EINVAL;
> +			goto release_raw;
>  		}
>  
>  		cfg.raw_pos += offset;
> @@ -1478,26 +1486,30 @@ static int mxt_update_cfg(struct mxt_data *data, const struct firmware *fw)
>  
>  	if (cfg.info.family_id != data->info->family_id) {
>  		dev_err(dev, "Family ID mismatch!\n");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto release_raw;
>  	}
>  
>  	if (cfg.info.variant_id != data->info->variant_id) {
>  		dev_err(dev, "Variant ID mismatch!\n");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto release_raw;
>  	}
>  
>  	/* Read CRCs */
>  	ret = sscanf(cfg.raw + cfg.raw_pos, "%x%n", &info_crc, &offset);
>  	if (ret != 1) {
>  		dev_err(dev, "Bad format: failed to parse Info CRC\n");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto release_raw;
>  	}
>  	cfg.raw_pos += offset;
>  
>  	ret = sscanf(cfg.raw + cfg.raw_pos, "%x%n", &config_crc, &offset);
>  	if (ret != 1) {
>  		dev_err(dev, "Bad format: failed to parse Config CRC\n");
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto release_raw;
>  	}
>  	cfg.raw_pos += offset;
>  
> @@ -1530,8 +1542,10 @@ static int mxt_update_cfg(struct mxt_data *data, const struct firmware *fw)
>  			MXT_INFO_CHECKSUM_SIZE;
>  	cfg.mem_size = data->mem_size - cfg.start_ofs;
>  	cfg.mem = kzalloc(cfg.mem_size, GFP_KERNEL);
> -	if (!cfg.mem)
> -		return -ENOMEM;
> +	if (!cfg.mem) {
> +		ret = -ENOMEM;
> +		goto release_raw;
> +	}
>  
>  	ret = mxt_prepare_cfg_mem(data, &cfg);
>  	if (ret)
> @@ -1570,6 +1584,8 @@ static int mxt_update_cfg(struct mxt_data *data, const struct firmware *fw)
>  	/* T7 config may have changed */
>  	mxt_init_t7_power_cfg(data);
>  
> +release_raw:
> +	kfree(cfg.raw);
>  release_mem:
>  	kfree(cfg.mem);
>  	return ret;
> -- 
> 2.17.1
> 

-- 
Dmitry