Commit ac68b1b3 authored Mar 09, 2018 by Luis R. Rodriguez Committed by Linus Torvalds Mar 09, 2018

lib/test_kmod.c: fix limit check on number of test devices created

As reported by Dan the parentheses is in the wrong place, and since
unlikely() call returns either 0 or 1 it's never less than zero.  The
second issue is that signed integer overflows like "INT_MAX + 1" are
undefined behavior.

Since num_test_devs represents the number of devices, we want to stop
prior to hitting the max, and not rely on the wrap arround at all.  So
just cap at num_test_devs + 1, prior to assigning a new device.

Link: http://lkml.kernel.org/r/20180224030046.24238-1-mcgrof@kernel.org


Fixes: d9c6a72d ("kmod: add test driver to stress test the module loader")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 0627be7d

lib/test_kmod.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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 + 1 == INT_MAX) {
		pr_err("reached limit of number of test devices\n");
		goto out;
		}

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