linux-kernel - [PATCH] lib/test_kmod: Fix an integer overflow test

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Message-ID: <20180122102754.GD23912@mwanda>
Date:   Mon, 22 Jan 2018 13:27:54 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] lib/test_kmod: Fix an integer overflow test

The main problem is that the parentheses are in the wrong place and the
unlikely() call returns either 0 or 1 so it's never less than zero.  The
other problem is that signed integer overflows like "INT_MAX + 1" are
undefined behavior.

Fixes: d9c6a72d6fa2 ("kmod: add test driver to stress test the module loader")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/lib/test_kmod.c b/lib/test_kmod.c
index e372b97eee13..30fd6d9e5361 100644
--- a/lib/test_kmod.c
+++ b/lib/test_kmod.c
@@ -1141,7 +1141,7 @@ static struct kmod_test_device *register_test_dev_kmod(void)
 	mutex_lock(&reg_dev_mutex);

 	/* int should suffice for number of devices, test for wrap */
-	if (unlikely(num_test_devs + 1) < 0) {
+	if (num_test_devs == INT_MAX) {
 		pr_err("reached limit of number of test devices\n");
 		goto out;
 	}