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Message-ID: <20190723162403.GA56959@lakrids.cambridge.arm.com>
Date: Tue, 23 Jul 2019 17:24:03 +0100
From: Mark Rutland <mark.rutland@....com>
To: Marco Elver <elver@...gle.com>
Cc: linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Alexander Potapenko <glider@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Andrey Konovalov <andreyknvl@...gle.com>,
Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
kasan-dev@...glegroups.com
Subject: Re: [PATCH 2/2] lib/test_kasan: Add stack overflow test
On Fri, Jul 19, 2019 at 03:28:18PM +0200, Marco Elver wrote:
> Adds a simple stack overflow test, to check the error being reported on
> an overflow. Without CONFIG_STACK_GUARD_PAGE, the result is typically
> some seemingly unrelated KASAN error message due to accessing random
> other memory.
Can't we use the LKDTM_EXHAUST_STACK case to check this?
I was also under the impression that the other KASAN self-tests weren't
fatal, and IIUC this will kill the kernel.
Given that, and given this is testing non-KASAN functionality, I'm not
sure it makes sense to bundle this with the KASAN tests.
Thanks,
Mark.
>
> Signed-off-by: Marco Elver <elver@...gle.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Cc: Alexander Potapenko <glider@...gle.com>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Andrey Konovalov <andreyknvl@...gle.com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: kasan-dev@...glegroups.com
> ---
> lib/test_kasan.c | 36 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index b63b367a94e8..3092ec01189d 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -15,6 +15,7 @@
> #include <linux/mman.h>
> #include <linux/module.h>
> #include <linux/printk.h>
> +#include <linux/sched/task_stack.h>
> #include <linux/slab.h>
> #include <linux/string.h>
> #include <linux/uaccess.h>
> @@ -709,6 +710,32 @@ static noinline void __init kmalloc_double_kzfree(void)
> kzfree(ptr);
> }
>
> +#ifdef CONFIG_STACK_GUARD_PAGE
> +static noinline void __init stack_overflow_via_recursion(void)
> +{
> + volatile int n = 512;
> +
> + BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
> +
> + /* About to overflow: overflow via alloca'd array and try to write. */
> + if (!object_is_on_stack((void *)&n - n)) {
> + volatile char overflow[n];
> +
> + overflow[0] = overflow[0];
> + return;
> + }
> +
> + stack_overflow_via_recursion();
> +}
> +
> +static noinline void __init kasan_stack_overflow(void)
> +{
> + pr_info("stack overflow begin\n");
> + stack_overflow_via_recursion();
> + pr_info("stack overflow end\n");
> +}
> +#endif
> +
> static int __init kmalloc_tests_init(void)
> {
> /*
> @@ -753,6 +780,15 @@ static int __init kmalloc_tests_init(void)
> kasan_bitops();
> kmalloc_double_kzfree();
>
> +#ifdef CONFIG_STACK_GUARD_PAGE
> + /*
> + * Only test with CONFIG_STACK_GUARD_PAGE, as without we get other
> + * random KASAN violations, due to accessing other random memory (we
> + * want to avoid actually corrupting memory in these tests).
> + */
> + kasan_stack_overflow();
> +#endif
> +
> kasan_restore_multi_shot(multishot);
>
> return -EAGAIN;
> --
> 2.22.0.657.g960e92d24f-goog
>
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