linux-kernel - [PATCH] tracing/user_events: Fix the incorrect trace record for null arguments events

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Message-Id: <20230601094158.575019-1-sunliming@kylinos.cn>
Date:   Thu,  1 Jun 2023 17:41:58 +0800
From:   sunliming <sunliming@...inos.cn>
To:     rostedt@...dmis.org, mhiramat@...nel.org, beaub@...ux.microsoft.com
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        sunliming <sunliming@...inos.cn>
Subject: [PATCH] tracing/user_events: Fix the incorrect trace record for null arguments events

The user_events support events that has null arguments. But the trace event
is discard and not really committed when the arguments is null, fix this
problem.

Signed-off-by: sunliming <sunliming@...inos.cn>
---
 kernel/trace/trace_events_user.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 0d91dac206ff..296bdfa674cb 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1399,7 +1399,7 @@ static void user_event_ftrace(struct user_event *user, struct iov_iter *i,
 	if (unlikely(!entry))
 		return;
 
-	if (unlikely(!copy_nofault(entry + 1, i->count, i)))
+	if (unlikely(i->count && !copy_nofault(entry + 1, i->count, i)))
 		goto discard;
 
 	if (!list_empty(&user->validators) &&
@@ -1440,7 +1440,7 @@ static void user_event_perf(struct user_event *user, struct iov_iter *i,
 
 		perf_fetch_caller_regs(regs);
 
-		if (unlikely(!copy_nofault(perf_entry + 1, i->count, i)))
+		if (unlikely(i->count && !copy_nofault(perf_entry + 1, i->count, i)))
 			goto discard;
 
 		if (!list_empty(&user->validators) &&
-- 
2.25.1