rtla: Replace atoi() with a robust strtoi()

The atoi() function does not perform error checking, which can lead to
undefined behavior when parsing invalid or out-of-range strings. This
can cause issues when parsing user-provided numerical inputs, such as
signal numbers, PIDs, or CPU lists.

To address this, introduce a new strtoi() helper function that safely
converts a string to an integer. This function validates the input and
checks for overflows, returning a negative value on  failure.

Replace all calls to atoi() with the new strtoi() function and add
proper error handling to make the parsing more robust and prevent
potential issues.

Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Link: https://lore.kernel.org/r/20260106133655.249887-5-wander@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>

tools/tracing/rtla/src/actions.c

@@ -181,12 +181,13 @@ actions_parse(struct actions *self, const char *trigger, const char *tracefn)
 		/* Takes two arguments, num (signal) and pid */
 		while (token != NULL) {
 			if (strlen(token) > 4 && strncmp(token, "num=", 4) == 0) {
-				signal = atoi(token + 4);
+				if (strtoi(token + 4, &signal))
+					return -1;
 			} else if (strlen(token) > 4 && strncmp(token, "pid=", 4) == 0) {
 				if (strncmp(token + 4, "parent", 7) == 0)
 					pid = -1;
-				else
-					pid = atoi(token + 4);
+				else if (strtoi(token + 4, &pid))
+					return -1;
 			} else {
 				/* Invalid argument */
 				return -1;

tools/tracing/rtla/src/utils.c

@@ -17,6 +17,7 @@
 #include <fcntl.h>
 #include <sched.h>
 #include <stdio.h>
+#include <limits.h>
 
 #include "utils.h"
 
@@ -127,16 +128,18 @@ int parse_cpu_set(char *cpu_list, cpu_set_t *set)
 	nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
 
 	for (p = cpu_list; *p; ) {
-		cpu = atoi(p);
-		if (cpu < 0 || (!cpu && *p != '0') || cpu >= nr_cpus)
+		if (strtoi(p, &cpu))
+			goto err;
+		if (cpu < 0 || cpu >= nr_cpus)
 			goto err;
 
 		while (isdigit(*p))
 			p++;
 		if (*p == '-') {
 			p++;
-			end_cpu = atoi(p);
-			if (end_cpu < cpu || (!end_cpu && *p != '0') || end_cpu >= nr_cpus)
+			if (strtoi(p, &end_cpu))
+				goto err;
+			if (end_cpu < cpu || end_cpu >= nr_cpus)
 				goto err;
 			while (isdigit(*p))
 				p++;
@@ -337,6 +340,7 @@ int set_comm_sched_attr(const char *comm_prefix, struct sched_attr *attr)
 	struct dirent *proc_entry;
 	DIR *procfs;
 	int retval;
+	int pid;
 
 	if (strlen(comm_prefix) >= MAX_PATH) {
 		err_msg("Command prefix is too long: %d < strlen(%s)\n",
@@ -356,8 +360,12 @@ int set_comm_sched_attr(const char *comm_prefix, struct sched_attr *attr)
 		if (!retval)
 			continue;
 
+		if (strtoi(proc_entry->d_name, &pid)) {
+			err_msg("'%s' is not a valid pid", proc_entry->d_name);
+			goto out_err;
+		}
 		/* procfs_is_workload_pid confirmed it is a pid */
-		retval = __set_sched_attr(atoi(proc_entry->d_name), attr);
+		retval = __set_sched_attr(pid, attr);
 		if (retval) {
 			err_msg("Error setting sched attributes for pid:%s\n", proc_entry->d_name);
 			goto out_err;
@@ -999,3 +1007,25 @@ char *parse_optional_arg(int argc, char **argv)
 		return NULL;
 	}
 }
+
+/*
+ * strtoi - convert string to integer with error checking
+ *
+ * Returns 0 on success, -1 if conversion fails or result is out of int range.
+ */
+int strtoi(const char *s, int *res)
+{
+	char *end_ptr;
+	long lres;
+
+	if (!*s)
+		return -1;
+
+	errno = 0;
+	lres = strtol(s, &end_ptr, 0);
+	if (errno || *end_ptr || lres > INT_MAX || lres < INT_MIN)
+		return -1;
+
+	*res = (int) lres;
+	return 0;
+}

tools/tracing/rtla/src/utils.h

@@ -3,6 +3,7 @@
 #include <stdint.h>
 #include <time.h>
 #include <sched.h>
+#include <stdbool.h>
 
 /*
  * '18446744073709551615\0'
@@ -81,6 +82,7 @@ static inline int set_deepest_cpu_idle_state(unsigned int cpu, unsigned int stat
 static inline int have_libcpupower_support(void) { return 0; }
 #endif /* HAVE_LIBCPUPOWER_SUPPORT */
 int auto_house_keeping(cpu_set_t *monitored_cpus);
+__attribute__((__warn_unused_result__)) int strtoi(const char *s, int *res);
 
 #define ns_to_usf(x) (((double)x/1000))
 #define ns_to_per(total, part) ((part * 100) / (double)total)