linux-kernel - [PATCH v2] tracing/string: Create and use __free(argv_free) in trace

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Message-ID: <20241220103313.4a74ec8e@gandalf.local.home>
Date: Fri, 20 Dec 2024 10:33:13 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Peter Zijlstra <peterz@...radead.org>,
 Kees Cook <kees@...nel.org>, Andy Shevchenko <andy@...nel.org>,
 linux-hardening@...r.kernel.org
Subject: [PATCH v2] tracing/string: Create and use __free(argv_free) in
 trace_dynevent.c

From: Steven Rostedt <rostedt@...dmis.org>

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@...nel.org>
Cc: Andy Shevchenko <andy@...nel.org>
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
Changes since v1: https://lore.kernel.org/all/20241219201346.029319524@goodmis.org/

- Moved include of cleanup.h up to be more alphabetically ordered

 include/linux/string.h        |  3 +++
 kernel/trace/trace_dynevent.c | 23 +++++++----------------
 2 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index 493ac4862c77..86d5d352068b 100644
--- 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 4376887e0d8a..a322e4f249a5 100644
--- 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;
 }
 
-- 
2.45.2