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From: Dave Martin <Dave.Martin@arm.com>
To: Cristian Marussi <cristian.marussi@arm.com>
Cc: linux-kselftest@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, shuah@kernel.org,
	andreyknvl@google.com
Subject: Re: [PATCH v3 10/11] kselftest: arm64: fake_sigreturn_bad_size
Date: Tue, 13 Aug 2019 17:26:46 +0100
Message-ID: <20190813162646.GH10425@arm.com> (raw)
In-Reply-To: <20190802170300.20662-11-cristian.marussi@arm.com>

On Fri, Aug 02, 2019 at 06:02:59PM +0100, Cristian Marussi wrote:
> Added a simple fake_sigreturn testcase which builds a ucontext_t

Add

> with a badly sized header that causes a overrun in the __reserved
> area and place it onto the stack. Expects a SIGSEGV on test PASS.
> 
> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> ---
>  .../arm64/signal/testcases/.gitignore         |  1 +
>  .../testcases/fake_sigreturn_bad_size.c       | 85 +++++++++++++++++++
>  2 files changed, 86 insertions(+)
>  create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
> 
> diff --git a/tools/testing/selftests/arm64/signal/testcases/.gitignore b/tools/testing/selftests/arm64/signal/testcases/.gitignore
> index 94f9baaf638c..3408e0f5ba98 100644
> --- a/tools/testing/selftests/arm64/signal/testcases/.gitignore
> +++ b/tools/testing/selftests/arm64/signal/testcases/.gitignore
> @@ -8,3 +8,4 @@ fake_sigreturn_bad_magic
>  fake_sigreturn_bad_size_for_magic0
>  fake_sigreturn_missing_fpsimd
>  fake_sigreturn_duplicated_fpsimd
> +fake_sigreturn_bad_size
> diff --git a/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
> new file mode 100644
> index 000000000000..1467fb534d8b
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
> @@ -0,0 +1,85 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (C) 2019 ARM Limited */
> +

signal.h?

> +#include <stdio.h>
> +#include <ucontext.h>
> +
> +#include "test_signals_utils.h"
> +#include "testcases.h"
> +
> +struct fake_sigframe sf;
> +
> +#define MIN_SZ_ALIGN	16
> +
> +static int fake_sigreturn_bad_size_run(struct tdescr *td,
> +				       siginfo_t *si, ucontext_t *uc)
> +{
> +	size_t resv_sz, need_sz, offset;
> +	struct _aarch64_ctx *shead = GET_SF_RESV_HEAD(sf), *head;
> +
> +	/* just to fill the ucontext_t with something real */
> +	if (!get_current_context(td, &sf.uc))
> +		return 1;
> +
> +	resv_sz = GET_SF_RESV_SIZE(sf);
> +	/*
> +	 * find the terminator, preserving existing headers
> +	 * and verify amount of spare room in __reserved area.
> +	 */
> +	head = get_terminator(shead, resv_sz, &offset);
> +	/*
> +	 * try stripping extra_context header when low on space:
> +	 * we need at least  for the bad sized esr_context.

double space

> +	 */
> +	need_sz = HDR_SZ + sizeof(struct esr_context);
> +	if (head && resv_sz - offset < need_sz) {
> +		fprintf(stderr, "Low on space:%zd. Discarding extra_context.\n",
> +			resv_sz - offset);
> +		head = get_header(shead, EXTRA_MAGIC, resv_sz, &offset);
> +	}
> +	/* just give up and timeout if still not enough space */
> +	if (head && resv_sz - offset >= need_sz) {
> +		fprintf(stderr, "Mangling template header. Spare space:%zd\n",
> +			resv_sz - offset);
> +		/*
> +		 * Use an esr_context to build a fake header with a
> +		 * size greater then the free __reserved area minus HDR_SZ;
> +		 * using ESR_MAGIC here since it is not checked for size nor
> +		 * is limited to one instance.
> +		 *
> +		 * At first inject an additional normal esr_context
> +		 */
> +		head->magic = ESR_MAGIC;
> +		head->size = sizeof(struct esr_context);
> +		/* and terminate properly */
> +		write_terminator_record(GET_RESV_NEXT_HEAD(head));
> +		ASSERT_GOOD_CONTEXT(&sf.uc);
> +
> +		/*
> +		 * now mess with fake esr_context size: leaving less space than
> +		 * neededwhile keeping size value 16-aligned
> +		 *
> +		 * It must trigger a SEGV from Kernel on:
> +		 *
> +		 *	resv_sz - offset < sizeof(*head)
> +		 */
> +		/* at first set the maximum good 16-aligned size */
> +		head->size = (resv_sz - offset - need_sz + MIN_SZ_ALIGN) & ~0xfUL;
> +		/* plus a bit more of 16-aligned sized stuff */
> +		head->size += MIN_SZ_ALIGN;
> +		/* and terminate properly */
> +		write_terminator_record(GET_RESV_NEXT_HEAD(head));
> +		ASSERT_BAD_CONTEXT(&sf.uc);
> +		fake_sigreturn(&sf, sizeof(sf), 16);
> +	}
> +
> +	return 1;
> +}

[...]

Otherwise looks reasonable.

Cheers
---Dave

  reply index

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02 17:02 [PATCH v3 00/11] Add arm64/signal initial kselftest support Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 01/11] kselftest: arm64: introduce new boilerplate code Cristian Marussi
2019-08-13 16:23   ` Dave Martin
2019-08-27 12:14     ` Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 02/11] kselftest: arm64: adds first test and common utils Cristian Marussi
2019-08-06 15:50   ` Cristian Marussi
2019-08-07 15:42   ` Cristian Marussi
2019-08-09 10:54   ` Cristian Marussi
2019-08-09 11:16     ` Dave Martin
2019-08-09 12:20       ` Cristian Marussi
2019-08-09 12:32         ` Dave Martin
2019-08-12 12:43   ` Amit Kachhap
2019-08-13 13:22     ` Cristian Marussi
2019-08-14 10:22       ` Amit Kachhap
2019-08-27 14:24         ` Cristian Marussi
2019-08-13 16:24   ` Dave Martin
2019-08-28 17:34     ` Cristian Marussi
2019-09-03 15:34       ` Dave Martin
2019-09-03 16:08         ` Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 03/11] kselftest: arm64: mangle_pstate_invalid_daif_bits Cristian Marussi
2019-08-13 16:24   ` Dave Martin
2019-08-29 10:19     ` Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 04/11] kselftest: arm64: mangle_pstate_invalid_mode_el Cristian Marussi
2019-08-13 16:24   ` Dave Martin
2019-08-29 11:50     ` Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 05/11] kselftest: arm64: mangle_pstate_ssbs_regs Cristian Marussi
2019-08-13 16:25   ` Dave Martin
2019-08-29 15:35     ` Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 06/11] kselftest: arm64: fake_sigreturn_bad_magic Cristian Marussi
2019-08-13 16:25   ` Dave Martin
2019-08-30 14:29     ` Cristian Marussi
2019-09-04 10:05       ` Dave Martin
2019-09-04 10:37         ` Cristian Marussi
2019-09-04 10:47           ` Dave Martin
2019-08-02 17:02 ` [PATCH v3 07/11] kselftest: arm64: fake_sigreturn_bad_size_for_magic0 Cristian Marussi
2019-08-13 16:25   ` Dave Martin
2019-08-30 14:49     ` Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 08/11] kselftest: arm64: fake_sigreturn_missing_fpsimd Cristian Marussi
2019-08-13 16:26   ` Dave Martin
2019-08-30 14:55     ` Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 09/11] kselftest: arm64: fake_sigreturn_duplicated_fpsimd Cristian Marussi
2019-08-13 16:26   ` Dave Martin
2019-08-30 15:11     ` Cristian Marussi
2019-08-02 17:02 ` [PATCH v3 10/11] kselftest: arm64: fake_sigreturn_bad_size Cristian Marussi
2019-08-13 16:26   ` Dave Martin [this message]
2019-08-30 15:21     ` Cristian Marussi
2019-08-02 17:03 ` [PATCH v3 11/11] kselftest: arm64: fake_sigreturn_misaligned_sp Cristian Marussi
2019-08-07 16:04   ` Cristian Marussi
2019-08-13 16:28     ` Dave Martin
2019-08-30 15:22       ` Cristian Marussi
2019-08-13 16:27   ` Dave Martin
2019-08-30 16:33     ` Cristian Marussi
2019-08-13 16:22 ` [PATCH v3 00/11] Add arm64/signal initial kselftest support Dave Martin
2019-08-30 16:40   ` Cristian Marussi
2019-09-02 10:53     ` Dave Martin
2019-09-02 11:30       ` Cristian Marussi

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