linux-kernel - [PATCH v2 01/28] module: Extend the preempt disabled section in dereference_symbol

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Message-ID: <20241220174731.514432-2-bigeasy@linutronix.de>
Date: Fri, 20 Dec 2024 18:41:15 +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>,
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Helge Deller <deller@....de>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Naveen N Rao <naveen@...nel.org>,
	Nicholas Piggin <npiggin@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	linux-parisc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 01/28] module: Extend the preempt disabled section in dereference_symbol_descriptor().

dereference_symbol_descriptor() needs to obtain the module pointer
belonging to pointer in order to resolve that pointer.
The returned mod pointer is obtained under RCU-sched/ preempt_disable()
guarantees and needs to be used within this section to ensure that the
module is not removed in the meantime.

Extend the preempt_disable() section to also cover
dereference_module_function_descriptor().

Fixes: 04b8eb7a4ccd9 ("symbol lookup: introduce dereference_symbol_descriptor()")
Cc: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Helge Deller <deller@....de>
Cc: Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Naveen N Rao <naveen@...nel.org>
Cc: Nicholas Piggin <npiggin@...il.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc: linux-parisc@...r.kernel.org
Cc: linuxppc-dev@...ts.ozlabs.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 include/linux/kallsyms.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index c3f075e8f60cb..1c6a6c1704d8d 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -57,10 +57,10 @@ static inline void *dereference_symbol_descriptor(void *ptr)
 
 	preempt_disable();
 	mod = __module_address((unsigned long)ptr);
-	preempt_enable();
 
 	if (mod)
 		ptr = dereference_module_function_descriptor(mod, ptr);
+	preempt_enable();
 #endif
 	return ptr;
 }
-- 
2.45.2