linux-kernel - [PATCH] ftrace: Initialize variables for ftrace_startup/shutdown

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Message-ID: <20250417104017.3aea66c2@gandalf.local.home>
Date: Thu, 17 Apr 2025 10:40:17 -0400
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>, Mark Rutland
 <mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
Subject: [PATCH] ftrace: Initialize variables for
 ftrace_startup/shutdown_subops()

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

The reworking to fix and simplify the ftrace_startup_subops() and the
ftrace_shutdown_subops() made it possible for the filter_hash and
notrace_hash variables to be used uninitialized in a way that the compiler
did not catch it.

Initialize both filter_hash and notrace_hash to the EMPTY_HASH as that is
what they should be if they never are used.

Reported-by: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
Fixes: 0ae6b8ce200d ("ftrace: Fix accounting of subop hashes")
Closes: https://lore.kernel.org/all/1db64a42-626d-4b3a-be08-c65e47333ce2@linux.ibm.com/
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/ftrace.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 19b902b8de2b..66bf4512ec04 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3490,8 +3490,8 @@ static int add_next_hash(struct ftrace_hash **filter_hash, struct ftrace_hash **
  */
 int ftrace_startup_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, int command)
 {
-	struct ftrace_hash *filter_hash;
-	struct ftrace_hash *notrace_hash;
+	struct ftrace_hash *filter_hash = EMPTY_HASH;
+	struct ftrace_hash *notrace_hash = EMPTY_HASH;
 	struct ftrace_hash *save_filter_hash;
 	struct ftrace_hash *save_notrace_hash;
 	int ret;
@@ -3625,8 +3625,8 @@ static int rebuild_hashes(struct ftrace_hash **filter_hash, struct ftrace_hash *
  */
 int ftrace_shutdown_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, int command)
 {
-	struct ftrace_hash *filter_hash;
-	struct ftrace_hash *notrace_hash;
+	struct ftrace_hash *filter_hash = EMPTY_HASH;
+	struct ftrace_hash *notrace_hash = EMPTY_HASH;
 	int ret;
 
 	if (unlikely(ftrace_disabled))
-- 
2.47.2