linux-kernel - [PATCH] ftrace: Reinitialize hash to EMPTY

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Message-ID: <20250417110933.20ab718b@gandalf.local.home>
Date: Thu, 17 Apr 2025 11:09:33 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>, Mathieu
 Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [PATCH] ftrace: Reinitialize hash to EMPTY_HASH after freeing

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

There's several locations that free a ftrace hash pointer but may be
referenced again. Reset them to EMPTY_HASH so that a u-a-f bug doesn't
happen.

Fixes: 0ae6b8ce200d ("ftrace: Fix accounting of subop hashes")
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/ftrace.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 66bf4512ec04..39ccbb3b9693 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1297,6 +1297,8 @@ void ftrace_free_filter(struct ftrace_ops *ops)
 		return;
 	free_ftrace_hash(ops->func_hash->filter_hash);
 	free_ftrace_hash(ops->func_hash->notrace_hash);
+	ops->func_hash->filter_hash = EMPTY_HASH;
+	ops->func_hash->notrace_hash = EMPTY_HASH;
 }
 EXPORT_SYMBOL_GPL(ftrace_free_filter);
 
@@ -3443,6 +3445,7 @@ static int add_next_hash(struct ftrace_hash **filter_hash, struct ftrace_hash **
 				  size_bits);
 		if (ret < 0) {
 			free_ftrace_hash(*filter_hash);
+			*filter_hash = EMPTY_HASH;
 			return ret;
 		}
 	}
@@ -3472,6 +3475,7 @@ static int add_next_hash(struct ftrace_hash **filter_hash, struct ftrace_hash **
 				     subops_hash->notrace_hash);
 		if (ret < 0) {
 			free_ftrace_hash(*notrace_hash);
+			*notrace_hash = EMPTY_HASH;
 			return ret;
 		}
 	}
-- 
2.47.2