linux-kernel - [PATCH for 4.9 59/59] lkdtm: Fix Oops when unloading the module

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Message-ID: <20170914155051.8289-59-alexander.levin@verizon.com>
Date:   Thu, 14 Sep 2017 15:51:21 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Juerg Haefliger <juerg.haefliger@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Subject: [PATCH for 4.9 59/59] lkdtm: Fix Oops when unloading the module

From: Juerg Haefliger <juerg.haefliger@....com>

[ Upstream commit 9ba60573638e2006170ebcc5489fb1e068afbc8f ]

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>
Acked-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.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 f9154b8d67f6..b2989f2d3126 100644
--- a/drivers/misc/lkdtm_core.c
+++ b/drivers/misc/lkdtm_core.c
@@ -533,7 +533,9 @@ 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