linux-kernel - [PATCH v4 04/18] jump_label,module: Fix module lifetime for __jump_label_mod_text

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Message-Id: <20200501202944.014486297@infradead.org>
Date:   Fri, 01 May 2020 22:28:53 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, mhiramat@...nel.org, bristot@...hat.com,
        jbaron@...mai.com, torvalds@...ux-foundation.org,
        tglx@...utronix.de, mingo@...nel.org, namit@...are.com,
        hpa@...or.com, luto@...nel.org, ard.biesheuvel@...aro.org,
        jpoimboe@...hat.com, pbonzini@...hat.com,
        mathieu.desnoyers@...icios.com
Subject: [PATCH v4 04/18] jump_label,module: Fix module lifetime for __jump_label_mod_text_reserved

Nothing ensures the module exists while we're iterating
mod->jump_entries in __jump_label_mod_text_reserved(), take a module
reference to ensure the module sticks around.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/jump_label.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -539,19 +539,25 @@ static void static_key_set_mod(struct st
 static int __jump_label_mod_text_reserved(void *start, void *end)
 {
 	struct module *mod;
+	int ret;
 
 	preempt_disable();
 	mod = __module_text_address((unsigned long)start);
 	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
+	if (!try_module_get(mod))
+		mod = NULL;
 	preempt_enable();
 
 	if (!mod)
 		return 0;
 
-
-	return __jump_label_text_reserved(mod->jump_entries,
+	ret = __jump_label_text_reserved(mod->jump_entries,
 				mod->jump_entries + mod->num_jump_entries,
 				start, end);
+
+	module_put(mod);
+
+	return ret;
 }
 
 static void __jump_label_mod_update(struct static_key *key)