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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,
	amit.kachhap@arm.com, andreyknvl@google.com
Subject: Re: [PATCH v5 10/11] kselftest: arm64: fake_sigreturn_bad_size
Date: Wed, 4 Sep 2019 12:49:33 +0100
Message-ID: <20190904114933.GA27757@arm.com> (raw)
In-Reply-To: <20190902112932.36129-11-cristian.marussi@arm.com>

On Mon, Sep 02, 2019 at 12:29:31pm +0100, Cristian Marussi wrote:
> Add a simple fake_sigreturn testcase which builds a ucontext_t 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>
> ---
> v3 --> v4
> - fix commit
> - missing include
> - using new get_starting_head() helper
> - added test description
> ---
>  .../testcases/fake_sigreturn_bad_size.c       | 77 +++++++++++++++++++
>  1 file changed, 77 insertions(+)
>  create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
> 
> 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..b1156afdb691
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
> @@ -0,0 +1,77 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 ARM Limited
> + *
> + * Place a fake sigframe on the stack including a bad record overflowing
> + * the __reserved space: on sigreturn Kernel must spot this attempt and
> + * the test case is expected to be terminated via SEGV.
> + */
> +
> +#include <signal.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);
> +	/* at least HDR_SZ + bad sized esr_context needed */
> +	need_sz = HDR_SZ + sizeof(struct esr_context);

Nit: can we write this sum the other way round (see comment on patch 9)?

> +	head = get_starting_head(shead, need_sz, resv_sz, &offset);
> +	if (head) {
> +		/*
> +		 * 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
> +		 * needed while 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;

Can we also have versions of this test that try:

 a) a size that doesn't overflow __reserved[], but is not a multiple of 16
 b) a size that is less than 16
 c) a size that does overflow __reserved[], but by less than 16 bytes?

These tests are all closely related and can probably be macro-ised
easily.  They can go on the TODO list for now anyway: let's get this
series settled in its current form first.

In any case:

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

  reply index

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-02 11:29 [PATCH v5 00/11] Add arm64/signal initial kselftest support Cristian Marussi
2019-09-02 11:29 ` [PATCH v5 01/11] kselftest: arm64: add skeleton Makefile Cristian Marussi
2019-09-03  9:26   ` Amit Kachhap
2019-09-03  9:45     ` Cristian Marussi
2019-09-05 17:57     ` Cristian Marussi
2019-09-09 12:42       ` Amit Kachhap
2019-09-16 11:41         ` Dave Martin
2019-09-04 11:47   ` Dave Martin
2019-09-05 13:45     ` Cristian Marussi
2019-09-05 14:18       ` Dave Martin
2019-09-02 11:29 ` [PATCH v5 02/11] kselftest: arm64: add common utils and one testcase Cristian Marussi
2019-09-04 11:47   ` Dave Martin
2019-09-06 10:26     ` Cristian Marussi
2019-09-16 11:40       ` Dave Martin
2019-09-02 11:29 ` [PATCH v5 03/11] kselftest: arm64: mangle_pstate_invalid_daif_bits Cristian Marussi
2019-09-04 11:48   ` Dave Martin
2019-09-02 11:29 ` [PATCH v5 04/11] kselftest: arm64: mangle_pstate_invalid_mode_el[123][ht] Cristian Marussi
2019-09-04 11:48   ` Dave Martin
2019-09-02 11:29 ` [PATCH v5 05/11] kselftest: arm64: mangle_pstate_ssbs_regs Cristian Marussi
2019-09-04 11:48   ` Dave Martin
2019-09-09 15:51     ` Cristian Marussi
2019-09-02 11:29 ` [PATCH v5 06/11] kselftest: arm64: fake_sigreturn_bad_magic Cristian Marussi
2019-09-04 11:48   ` Dave Martin
2019-09-09 17:31     ` Cristian Marussi
2019-09-02 11:29 ` [PATCH v5 07/11] kselftest: arm64: fake_sigreturn_bad_size_for_magic0 Cristian Marussi
2019-09-04 11:49   ` Dave Martin
2019-09-09 17:47     ` Cristian Marussi
2019-09-02 11:29 ` [PATCH v5 08/11] kselftest: arm64: fake_sigreturn_missing_fpsimd Cristian Marussi
2019-09-04 11:49   ` Dave Martin
2019-09-09 17:51     ` Cristian Marussi
2019-09-02 11:29 ` [PATCH v5 09/11] kselftest: arm64: fake_sigreturn_duplicated_fpsimd Cristian Marussi
2019-09-04 11:49   ` Dave Martin
2019-09-05 12:15     ` Cristian Marussi
2019-09-05 12:39       ` Dave Martin
2019-09-05 13:32         ` Cristian Marussi
2019-09-05 14:20           ` Dave Martin
2019-09-09 18:03     ` Cristian Marussi
2019-09-02 11:29 ` [PATCH v5 10/11] kselftest: arm64: fake_sigreturn_bad_size Cristian Marussi
2019-09-04 11:49   ` Dave Martin [this message]
2019-09-09 18:11     ` Cristian Marussi
2019-09-02 11:29 ` [PATCH v5 11/11] kselftest: arm64: fake_sigreturn_misaligned_sp Cristian Marussi
2019-09-04 11:49   ` Dave Martin
2019-09-09 18:32     ` Cristian Marussi
2019-09-04 11:47 ` [PATCH v5 00/11] Add arm64/signal initial kselftest support Dave Martin
2019-09-10 12:25   ` Cristian Marussi
2019-09-16 12:14     ` Dave Martin

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