linux-kernel - [PATCH V2 1/4] tracing/user_events: Fix the incorrect trace record for empty arguments events

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Date:   Mon,  5 Jun 2023 15:30:20 +0800
From:   sunliming <sunliming@...inos.cn>
To:     mhiramat@...nel.org, beaub@...ux.microsoft.com,
        rostedt@...dmis.org, shuah@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, kelulanainsley@...il.com,
        sunliming <sunliming@...inos.cn>
Subject: [PATCH V2 1/4] tracing/user_events: Fix the incorrect trace record for empty arguments events

The user_events support events that has empty arguments. But the trace event
is discarded and not really committed when the arguments is empty. Fix this
by not attempting to copy in zero-length data.

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..698703a3d234 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 != 0 && !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 != 0 && !copy_nofault(perf_entry + 1, i->count, i)))
 			goto discard;
 
 		if (!list_empty(&user->validators) &&
-- 
2.25.1