[v2] [RFC] dpaa2: replace system("echo ...") with file i/o

[Mattias Rönnblom]

On 2023-05-02 11:54, Sachin Saxena (OSS) wrote:
> From: Stephen Hemminger <stephen at networkplumber.org>
> 
>   Using system() is a bad idea in driver code because it introduces
>   a number of potential security issues. The codeql analysis tool
>   flags this a potential security issue.
> 
>   Instead just use normal stdio to do the same thing.
> 
>   Compile test only, do not have this hardware and therefore can
>   not test this.
> 
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> Reviewed-by: Sachin Saxena <sachin.saxena at oss.nxp.com>
> ---
>   drivers/bus/fslmc/portal/dpaa2_hw_dpio.c | 45 ++++++++++++++++--------
>   1 file changed, 31 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/bus/fslmc/portal/dpaa2_hw_dpio.c b/drivers/bus/fslmc/portal/dpaa2_hw_dpio.c
> index 4aec7b2cd8..990cfc5d3b 100644
> --- a/drivers/bus/fslmc/portal/dpaa2_hw_dpio.c
> +++ b/drivers/bus/fslmc/portal/dpaa2_hw_dpio.c
> @@ -125,14 +125,21 @@ static void
>   dpaa2_affine_dpio_intr_to_respective_core(int32_t dpio_id, int cpu_id)
>   {
>   #define STRING_LEN	28
> -#define COMMAND_LEN	50
> +#define AFFINITY_LEN	128
> +#define CMD_LEN	300
>   	uint32_t cpu_mask = 1;
> -	int ret;
> -	size_t len = 0;
> -	char *temp = NULL, *token = NULL;
> -	char string[STRING_LEN], command[COMMAND_LEN];
> +	size_t len = CMD_LEN;
> +	char *temp, *token = NULL;
> +	char string[STRING_LEN];
> +	char smp_affinity[AFFINITY_LEN];
>   	FILE *file;
>   
> +	temp = (char *)malloc(len * sizeof(char));

No cast is necessary to go from void * to any other pointer.

sizeof(char) is by definition one. What you allocate from the heap are 
in units of chars, so multiplying with sizeof(char) doesn't make sense.

How is pre-allocating the buffer an improvement over the old code 
(deferring memory allocation to getline())?

> +	if (temp == NULL) {
> +		DPAA2_BUS_WARN("Unable to allocate temp buffer");
> +		return;
> +	}
> +
>   	snprintf(string, STRING_LEN, "dpio.%d", dpio_id);
>   	file = fopen("/proc/interrupts", "r");
>   	if (!file) {
> @@ -155,17 +162,27 @@ dpaa2_affine_dpio_intr_to_respective_core(int32_t dpio_id, int cpu_id)
>   	}
>   
>   	cpu_mask = cpu_mask << cpu_id;
> -	snprintf(command, COMMAND_LEN, "echo %X > /proc/irq/%s/smp_affinity",
> -		 cpu_mask, token);
> -	ret = system(command);
> -	if (ret < 0)
> -		DPAA2_BUS_DEBUG(
> -			"Failed to affine interrupts on respective core");
> -	else
> -		DPAA2_BUS_DEBUG(" %s command is executed", command);
> -
> +	snprintf(smp_affinity, AFFINITY_LEN,
> +		 "/proc/irq/%s/smp_affinity", token);
> +	/* Free 'temp' memory after using the substring 'token' */
>   	free(temp);
>   	fclose(file);
> +
> +	file = fopen(smp_affinity, "w");
> +	if (file == NULL) {
> +		DPAA2_BUS_WARN("Failed to open %s", smp_affinity);
> +		return;
> +	}
> +	fprintf(file, "%X\n", cpu_mask);
> +	fflush(file);
> +
> +	if (ferror(file)) {
> +		fclose(file);
> +		DPAA2_BUS_WARN("Failed to write to %s", smp_affinity);
> +		return;
> +	}
> +
> +	fclose(file);
>   }
>   
>   static int dpaa2_dpio_intr_init(struct dpaa2_dpio_dev *dpio_dev)