linux-kernel - [PATCH] lkdtm: Fix Oops when unloading the module

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Date:   Thu, 19 Jan 2017 11:40:13 +0100
From:   Juerg Haefliger <juerg.haefliger@....com>
To:     keescook@...omium.org, linux-kernel@...r.kernel.org
Cc:     Juerg Haefliger <juerg.haefliger@....com>
Subject: [PATCH] lkdtm: Fix Oops when unloading the module

No jprobe is registered when the module is loaded without specifying a
crashpoint that uses a jprobe. At the moment, we unconditionally try to
unregister the jprobe on module unload which results in an Oops. Add a
check to fix this.

Signed-off-by: Juerg Haefliger <juerg.haefliger@....com>
---
 drivers/misc/lkdtm_core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c
index 7eeb71a75549..4d44084071d8 100644
--- a/drivers/misc/lkdtm_core.c
+++ b/drivers/misc/lkdtm_core.c
@@ -535,7 +535,9 @@ static void __exit lkdtm_module_exit(void)
 	/* Handle test-specific clean-up. */
 	lkdtm_usercopy_exit();
 
-	unregister_jprobe(lkdtm_jprobe);
+	if (lkdtm_jprobe != NULL)
+		unregister_jprobe(lkdtm_jprobe);
+
 	pr_info("Crash point unregistered\n");
 }
 
-- 
2.11.0