fix(dracut-util): avoid memory leak

The content of the kernel command line is assigned via `strdup`, but not freed
on exit. This happens after each call to `getarg(s)`, what makes an interesting
amount of bytes not released at every boot.

```
master> grep -r -o -e getarg -e getargs modules.d | wc -l
457
master> export CMDLINE=$(< /proc/cmdline)
master> echo ${#CMDLINE}
130
afeijoo@localhost:~/src/dracut/opensuse-fork/master> valgrind --leak-check=full --show-leak-kinds=all ./dracut-getarg security
==24270== Memcheck, a memory error detector
==24270== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==24270== Using Valgrind-3.20.0 and LibVEX; rerun with -h for copyright info
==24270== Command: ./dracut-getarg security
==24270==
apparmor
==24270==
==24270== HEAP SUMMARY:
==24270==     in use at exit: 131 bytes in 1 blocks
==24270==   total heap usage: 2 allocs, 1 frees, 1,155 bytes allocated
==24270==
==24270== 131 bytes in 1 blocks are definitely lost in loss record 1 of 1
==24270==    at 0x4838744: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==24270==    by 0x490D839: strdup (in /lib64/libc-2.31.so)
==24270==    by 0x108AF6: getarg (util.c:188)
==24270==    by 0x108AF6: main (util.c:300)
==24270==
==24270== LEAK SUMMARY:
==24270==    definitely lost: 131 bytes in 1 blocks
==24270==    indirectly lost: 0 bytes in 0 blocks
==24270==      possibly lost: 0 bytes in 0 blocks
==24270==    still reachable: 0 bytes in 0 blocks
==24270==         suppressed: 0 bytes in 0 blocks
==24270==
==24270== For lists of detected and suppressed errors, rerun with: -s
==24270== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
```

src/util/util.c

@@ -2,10 +2,11 @@
 
 // Parts are copied from the linux kernel
 
+#include <errno.h>
+#include <stdbool.h>
 #include <stdio.h>
-#include <string.h>
 #include <stdlib.h>
-#include <stdbool.h>
+#include <string.h>
 
 // CODE FROM LINUX KERNEL START
 
@@ -56,6 +57,13 @@ static char *skip_spaces(const char *str)
         return (char *)str;
 }
 
+#define _cleanup_(x) __attribute__((cleanup(x)))
+static inline void freep(void *p)
+{
+        free(*(void **)p);
+}
+#define _cleanup_free_ _cleanup_(freep)
+
 /*
  * Parse a string to get a param value pair.
  * You can use " around spaces, but can't escape ".
@@ -179,17 +187,20 @@ static int getarg(int argc, char **argv)
         char *search_value;
         char *end_value = NULL;
         bool bool_value = false;
-        char *cmdline = NULL;
+        _cleanup_free_ char *cmdline = NULL;
+        char *args = NULL;
+
+        if (argc != 2) {
+                usage(GETARG, EXIT_FAILURE, "Number of arguments invalid");
+        }
 
         char *p = getenv("CMDLINE");
         if (p == NULL) {
                 usage(GETARG, EXIT_FAILURE, "CMDLINE env not set");
         }
         cmdline = strdup(p);
-
-        if (argc != 2) {
-                usage(GETARG, EXIT_FAILURE, "Number of arguments invalid");
-        }
+        if (!cmdline)
+                return -ENOMEM;
 
         search_key = argv[1];
 
@@ -204,9 +215,10 @@ static int getarg(int argc, char **argv)
         if (strlen(search_key) == 0)
                 usage(GETARG, EXIT_FAILURE, "search key undefined");
 
+        args = cmdline;
         do {
                 char *key = NULL, *value = NULL;
-                cmdline = next_arg(cmdline, &key, &value);
+                args = next_arg(args, &key, &value);
                 if (strcmp(key, search_key) == 0) {
                         if (value) {
                                 end_value = value;
@@ -216,7 +228,7 @@ static int getarg(int argc, char **argv)
                                 bool_value = true;
                         }
                 }
-        } while (cmdline[0]);
+        } while (args[0]);
 
         if (search_value) {
                 if (end_value && strcmp(end_value, search_value) == 0) {
@@ -243,17 +255,20 @@ static int getargs(int argc, char **argv)
         char *search_key;
         char *search_value;
         bool found_value = false;
-        char *cmdline = NULL;
+        _cleanup_free_ char *cmdline = NULL;
+        char *args = NULL;
+
+        if (argc != 2) {
+                usage(GETARGS, EXIT_FAILURE, "Number of arguments invalid");
+        }
 
         char *p = getenv("CMDLINE");
         if (p == NULL) {
                 usage(GETARGS, EXIT_FAILURE, "CMDLINE env not set");
         }
         cmdline = strdup(p);
-
-        if (argc != 2) {
-                usage(GETARGS, EXIT_FAILURE, "Number of arguments invalid");
-        }
+        if (!cmdline)
+                return -ENOMEM;
 
         search_key = argv[1];
 
@@ -268,9 +283,10 @@ static int getargs(int argc, char **argv)
         if (strlen(search_key) == 0)
                 usage(GETARGS, EXIT_FAILURE, "search key undefined");
 
+        args = cmdline;
         do {
                 char *key = NULL, *value = NULL;
-                cmdline = next_arg(cmdline, &key, &value);
+                args = next_arg(args, &key, &value);
                 if (strcmp(key, search_key) == 0) {
                         if (search_value) {
                                 if (strcmp(value, search_value) == 0) {
@@ -286,7 +302,7 @@ static int getargs(int argc, char **argv)
                                 found_value = true;
                         }
                 }
-        } while (cmdline[0]);
+        } while (args[0]);
         return found_value ? EXIT_SUCCESS : EXIT_FAILURE;
 }