[PATCH AUTOSEL 6.1 02/12] tracing/user_events: Prevent same name but different args event

[Sasha Levin <sashal@xxxxxxxxxx>]

From: sunliming <sunliming@xxxxxxxxxx>

[ Upstream commit ba470eebc2f6c2f704872955a715b9555328e7d0 ]

User processes register name_args for events. If the same name but different
args event are registered. The trace outputs of second event are printed
as the first event. This is incorrect.

Return EADDRINUSE back to the user process if the same name but different args
event has being registered.

Link: https://lore.kernel.org/linux-trace-kernel/20230529032100.286534-1-sunliming@xxxxxxxxxx

Signed-off-by: sunliming <sunliming@xxxxxxxxxx>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Acked-by: Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/trace/trace_events_user.c              | 36 +++++++++++++++----
 .../selftests/user_events/ftrace_test.c       |  6 ++++
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 625cab4b9d945..774d146c2c2ca 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1274,6 +1274,8 @@ static int user_event_parse(struct user_event_group *group, char *name,
 	int index;
 	u32 key;
 	struct user_event *user;
+	int argc = 0;
+	char **argv;
 
 	/* Prevent dyn_event from racing */
 	mutex_lock(&event_mutex);
@@ -1281,13 +1283,35 @@ static int user_event_parse(struct user_event_group *group, char *name,
 	mutex_unlock(&event_mutex);
 
 	if (user) {
-		*newuser = user;
-		/*
-		 * Name is allocated by caller, free it since it already exists.
-		 * Caller only worries about failure cases for freeing.
-		 */
-		kfree(name);
+		if (args) {
+			argv = argv_split(GFP_KERNEL, args, &argc);
+			if (!argv) {
+				ret = -ENOMEM;
+				goto error;
+			}
+
+			ret = user_fields_match(user, argc, (const char **)argv);
+			argv_free(argv);
+
+		} else
+			ret = list_empty(&user->fields);
+
+		if (ret) {
+			*newuser = user;
+			/*
+			 * Name is allocated by caller, free it since it already exists.
+			 * Caller only worries about failure cases for freeing.
+			 */
+			kfree(name);
+		} else {
+			ret = -EADDRINUSE;
+			goto error;
+		}
+
 		return 0;
+error:
+		refcount_dec(&user->refcnt);
+		return ret;
 	}
 
 	index = find_first_zero_bit(group->page_bitmap, MAX_EVENTS);
diff --git a/tools/testing/selftests/user_events/ftrace_test.c b/tools/testing/selftests/user_events/ftrace_test.c
index 1bc26e6476fc3..df0e776c2cc1b 100644
--- a/tools/testing/selftests/user_events/ftrace_test.c
+++ b/tools/testing/selftests/user_events/ftrace_test.c
@@ -209,6 +209,12 @@ TEST_F(user, register_events) {
 	ASSERT_EQ(0, reg.write_index);
 	ASSERT_NE(0, reg.status_bit);
 
+	/* Multiple registers to same name but different args should fail */
+	reg.enable_bit = 29;
+	reg.name_args = (__u64)"__test_event u32 field1;";
+	ASSERT_EQ(-1, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
+	ASSERT_EQ(EADDRINUSE, errno);
+
 	/* Ensure disabled */
 	self->enable_fd = open(enable_file, O_RDWR);
 	ASSERT_NE(-1, self->enable_fd);
-- 
2.39.2