linux-kernel - some problems about kasan

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Message-ID: <561F4EEA.60203@huawei.com>
Date:	Thu, 15 Oct 2015 14:59:54 +0800
From:	zhong jiang <zhongjiang@...wei.com>
To:	<akpm@...ux-foundation.org>, <adech.fo@...il.com>,
	<ryabinin.a.a@...il.com>
CC:	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	<kasan-dev@...glegroups.com>, <qiuxishi@...wei.com>,
	<guohanjun@...wei.com>, <zhangdianfang@...wei.com>
Subject: some problems about kasan

1、 I feel confused about one of the cases when  testing the cases  kasan can solve . the function come from the kernel in the /lib/test_kasan.c.

  static noinline void __init kmalloc_uaf2(void)
{
	char *ptr1, *ptr2;
	size_t size = 43;

	pr_info("use-after-free after another kmalloc\n");
	ptr1 = kmalloc(size, GFP_KERNEL);
	if (!ptr1) {
		pr_err("Allocation failed\n");
		return;
	}

	kfree(ptr1);
	ptr2 = kmalloc(size, GFP_KERNEL);
	if (!ptr2) {
		pr_err("Allocation failed\n");
		return;
	}

	ptr1[40] = 'x';
	kfree(ptr2);
}

In the above function, the point ptr1 are probably  the same as the ptr2 . so the error not certain to occur.

2、Is the stack local variable out of bound access set by the GCC  ? I don't see any operate in the kernel

3、I want to know that the global variable size include redzone is allocated by the module_alloc().

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