From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 8 Jan 2025 09:04:43 +0000 (+0100)
Subject: module: Use RCU in all users of __module_address().
X-Git-Tag: v6.15-rc1~94^2~18
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6593a2c990f251bce63ab8de0397405303e32381;p=thirdparty%2Flinux.git

module: Use RCU in all users of __module_address().

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

Replace the preempt_disable() section around __module_address() with
RCU.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250108090457.512198-15-bigeasy@linutronix.de
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
---

diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index 1c6a6c1704d8d..d5dd54c53ace6 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -55,12 +55,11 @@ static inline void *dereference_symbol_descriptor(void *ptr)
 	if (is_ksym_addr((unsigned long)ptr))
 		return ptr;
 
-	preempt_disable();
+	guard(rcu)();
 	mod = __module_address((unsigned long)ptr);
 
 	if (mod)
 		ptr = dereference_module_function_descriptor(mod, ptr);
-	preempt_enable();
 #endif
 	return ptr;
 }
diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index 0e8ec6486d95c..00a60796327c0 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -316,7 +316,7 @@ void * __weak dereference_module_function_descriptor(struct module *mod,
 
 /*
  * For kallsyms to ask for address resolution.  NULL means not found.  Careful
- * not to lock to avoid deadlock on oopses, simply disable preemption.
+ * not to lock to avoid deadlock on oopses, RCU is enough.
  */
 int module_address_lookup(unsigned long addr,
 			  unsigned long *size,
@@ -330,7 +330,6 @@ int module_address_lookup(unsigned long addr,
 	struct module *mod;
 
 	guard(rcu)();
-	preempt_disable();
 	mod = __module_address(addr);
 	if (mod) {
 		if (modname)
@@ -348,8 +347,6 @@ int module_address_lookup(unsigned long addr,
 		if (sym)
 			ret = strscpy(namebuf, sym, KSYM_NAME_LEN);
 	}
-	preempt_enable();
-
 	return ret;
 }
 
diff --git a/kernel/module/main.c b/kernel/module/main.c
index aebb17e1bfb97..8a8b499730d86 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -3731,13 +3731,8 @@ const struct exception_table_entry *search_module_extables(unsigned long addr)
  */
 bool is_module_address(unsigned long addr)
 {
-	bool ret;
-
-	preempt_disable();
-	ret = __module_address(addr) != NULL;
-	preempt_enable();
-
-	return ret;
+	guard(rcu)();
+	return __module_address(addr) != NULL;
 }
 
 /**