linux-kernel - [PATCH v2 28/28] cfi: Use RCU while invoking __module

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Message-ID: <20241220174731.514432-29-bigeasy@linutronix.de>
Date: Fri, 20 Dec 2024 18:41:42 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: linux-modules@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Daniel Gomez <da.gomez@...sung.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Pavlu <petr.pavlu@...e.com>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Elliot Berman <quic_eberman@...cinc.com>,
	Kees Cook <kees@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	llvm@...ts.linux.dev
Subject: [PATCH v2 28/28] cfi: Use RCU while invoking __module_address().

__module_address() can be invoked within a RCU section, there is no
requirement to have preemption disabled.

I'm not sure if using rcu_read_lock() will introduce the regression that
has been fixed in commit 14c4c8e41511a ("cfi: Use
rcu_read_{un}lock_sched_notrace").

Cc: Elliot Berman <quic_eberman@...cinc.com>
Cc: Kees Cook <kees@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: llvm@...ts.linux.dev
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/cfi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/cfi.c b/kernel/cfi.c
index 08caad7767176..c8f2b5a51b2e6 100644
--- a/kernel/cfi.c
+++ b/kernel/cfi.c
@@ -71,6 +71,10 @@ static bool is_module_cfi_trap(unsigned long addr)
 	struct module *mod;
 	bool found = false;
 
+	/*
+	 * XXX this could be RCU protected but would it introcude the regression
+	 * fixed in 14c4c8e41511a ("cfi: Use rcu_read_{un}lock_sched_notrace")
+	 */
 	rcu_read_lock_sched_notrace();
 
 	mod = __module_address(addr);
-- 
2.45.2