[tip: core/static_call] jump_label,module: Fix module lifetime for __jump_label_mod_text_reserved()

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the core/static_call branch of tip:

Commit-ID:     0db6e3734b130207026df1e78455fa98ca1d6f50
Gitweb:        https://git.kernel.org/tip/0db6e3734b130207026df1e78455fa98ca1d6f50
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Tue, 18 Aug 2020 15:57:39 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 01 Sep 2020 09:58:04 +02:00

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@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200818135804.504501338@xxxxxxxxxxxxx
---
 kernel/jump_label.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index cdb3ffa..e661c61 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -539,19 +539,25 @@ static void static_key_set_mod(struct static_key *key,
 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)