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

[Sachin Saxena (OSS)]

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));
+	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)
-- 
2.25.1