trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump

The function simple_strtoul performs no error checking in scenarios
where the input value overflows the intended output variable.
This results in this function successfully returning, even when the
output does not match the input string (aka the function returns
successfully even when the result is wrong).

Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
simple_strtoul(), and simple_strtoull() functions explicitly ignore
overflows, which may lead to unexpected results in callers."
Hence, the use of those functions is discouraged.

This patch replaces all uses of the simple_strtoul with the safer
alternatives kstrtoint and kstrtol.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull

Signed-off-by: Yuran Pereira <[email protected]>
Reviewed-by: Douglas Anderson <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Steven Rostedt (Google) <[email protected]>
[nir: style fixes]
Signed-off-by: Nir Lichtman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Daniel Thompson <[email protected]>

Author: yuranpereira

kernel/trace/trace_kdb.c

@@ -96,22 +96,19 @@ static int kdb_ftdump(int argc, const char **argv)
 {
 	int skip_entries = 0;
 	long cpu_file;
-	char *cp;
+	int err;
 	int cnt;
 	int cpu;
 
 	if (argc > 2)
 		return KDB_ARGCOUNT;
 
-	if (argc) {
-		skip_entries = simple_strtol(argv[1], &cp, 0);
-		if (*cp)
-			skip_entries = 0;
-	}
+	if (argc && kstrtoint(argv[1], 0, &skip_entries))
+		return KDB_BADINT;
 
 	if (argc == 2) {
-		cpu_file = simple_strtol(argv[2], &cp, 0);
-		if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
+		err = kstrtol(argv[2], 0, &cpu_file);
+		if (err || cpu_file >= NR_CPUS || cpu_file < 0 ||
 		    !cpu_online(cpu_file))
 			return KDB_BADINT;
 	} else {