On Mon, 6 Nov 2023 17:28:11 -0500
Steven Rostedt [off-list ref] wrote:

On Sat,  4 Nov 2023 01:05:34 +0900
"Masami Hiramatsu (Google)" [off-list ref] wrote:

quoted

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Fix to check the tracepoint event is not valid with $retval.
The commit 08c9306fc2e3 ("tracing/fprobe-event: Assume fprobe is
a return event by $retval") introduced automatic return probe
conversion with $retval. But since tracepoint event does not
support return probe, $retval is not acceptable.

Can you add the command that causes this to fail.

Actually this doesn't command fail but it expected to fail.

$ echo "t kfree $retval" >> dynamic_events

This should be rejected because 't' (tracepoint) should not be
a return probe. Without this fix, this is accepted.
(But it traces a random return value because the tracepoint function
will return 'void'.)

Thank you,

-- Steve

quoted

Fixes: 08c9306fc2e3 ("tracing/fprobe-event: Assume fprobe is a return event by $retval")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 kernel/trace/trace_fprobe.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 8bfe23af9c73..7d2ddbcfa377 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c

@@ -927,11 +927,12 @@ static int parse_symbol_and_return(int argc, const char *argv[],
 	for (i = 2; i < argc; i++) {
 		tmp = strstr(argv[i], "$retval");
 		if (tmp && !isalnum(tmp[7]) && tmp[7] != '_') {
+			if (is_tracepoint) {
+				trace_probe_log_set_index(i);
+				trace_probe_log_err(tmp - argv[i], RETVAL_ON_PROBE);
+				return -EINVAL;
+			}
 			*is_return = true;
-			/*
-			 * NOTE: Don't check is_tracepoint here, because it will
-			 * be checked when the argument is parsed.
-			 */
 			break;
 		}
 	}

-- 
Masami Hiramatsu (Google) [off-list ref]