tracing/string: Create and use __free(argv_free) in trace_dynevent.c

The function dyn_event_release() uses argv_split() which must be freed via
argv_free(). It contains several error paths that do a goto out to call
argv_free() for cleanup. This makes the code complex and error prone.

Create a new __free() directive __free(argv_free) that will call
argv_free() for data allocated with argv_split(), and use it in the
dyn_event_release() function.

Cc: Kees Cook <kees@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: linux-hardening@vger.kernel.org
Link: https://lore.kernel.org/20241220103313.4a74ec8e@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/include/linux/string.h b/include/linux/string.h
index 493ac4862c77771ada8f12737277204e475eecc3..86d5d352068bbf18cbeec56d419688755e24f934 100644 (file)
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -4,6 +4,7 @@
 
 #include <linux/args.h>
 #include <linux/array_size.h>
+#include <linux/cleanup.h>     /* for DEFINE_FREE() */
 #include <linux/compiler.h>    /* for inline */
 #include <linux/types.h>       /* for size_t */
 #include <linux/stddef.h>      /* for NULL */
@@ -312,6 +313,8 @@ extern void *kmemdup_array(const void *src, size_t count, size_t element_size, g
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
 extern void argv_free(char **argv);
 
+DEFINE_FREE(argv_free, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
+
 /* lib/cmdline.c */
 extern int get_option(char **str, int *pint);
 extern char *get_options(const char *str, int nints, int *ints);

diff --git a/kernel/trace/trace_dynevent.c b/kernel/trace/trace_dynevent.c
index 4376887e0d8aabea0b3ac9fe96282e42cd853c61..a322e4f249a50334eda57cbe99997a9e9858ae12 100644 (file)
--- a/kernel/trace/trace_dynevent.c
+++ b/kernel/trace/trace_dynevent.c
@@ -74,24 +74,19 @@ int dyn_event_release(const char *raw_command, struct dyn_event_operations *type
        struct dyn_event *pos, *n;
        char *system = NULL, *event, *p;
        int argc, ret = -ENOENT;
-       char **argv;
+       char **argv __free(argv_free) = argv_split(GFP_KERNEL, raw_command, &argc);
 
-       argv = argv_split(GFP_KERNEL, raw_command, &argc);
        if (!argv)
                return -ENOMEM;
 
        if (argv[0][0] == '-') {
-               if (argv[0][1] != ':') {
-                       ret = -EINVAL;
-                       goto out;
-               }
+               if (argv[0][1] != ':')
+                       return -EINVAL;
                event = &argv[0][2];
        } else {
                event = strchr(argv[0], ':');
-               if (!event) {
-                       ret = -EINVAL;
-                       goto out;
-               }
+               if (!event)
+                       return -EINVAL;
                event++;
        }
 
@@ -101,10 +96,8 @@ int dyn_event_release(const char *raw_command, struct dyn_event_operations *type
                event = p + 1;
                *p = '\0';
        }
-       if (!system && event[0] == '\0') {
-               ret = -EINVAL;
-               goto out;
-       }
+       if (!system && event[0] == '\0')
+               return -EINVAL;
 
        mutex_lock(&event_mutex);
        for_each_dyn_event_safe(pos, n) {
@@ -120,8 +113,6 @@ int dyn_event_release(const char *raw_command, struct dyn_event_operations *type
        }
        tracing_reset_all_online_cpus();
        mutex_unlock(&event_mutex);
-out:
-       argv_free(argv);
        return ret;
 }