Subject: Re: [PATCH v5 07/11] kselftest: arm64: fake_sigreturn_bad_size_for_magic0

From: Dave Martin <[email-masked]>
Date: Wed, 4 Sep 2019 12:49:01 +0100

On Mon, Sep 02, 2019 at 12:29:28pm +0100, Cristian Marussi wrote:
> Add a simple fake_sigreturn testcase which builds a ucontext_t with a
> badly sized terminator record and place it onto the stack.
> Expects a SIGSEGV on test PASS.
> 
> Signed-off-by: Cristian Marussi <[email-masked]>
> ---
> v3 --> v4
> - fix commit
> - add signal.h include
> - using new get_starting_head() helper
> - added test description
> ---
>  .../fake_sigreturn_bad_size_for_magic0.c      | 49 +++++++++++++++++++
>  1 file changed, 49 insertions(+)
>  create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size_for_magic0.c
> 
> diff --git a/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size_for_magic0.c b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size_for_magic0.c
> new file mode 100644
> index 000000000000..25017fe18214
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size_for_magic0.c
> @@ -0,0 +1,49 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 ARM Limited
> + *
> + * Place a fake sigframe on the stack including a badly sized terminator
> + * record: 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;
> +
> +static int fake_sigreturn_bad_size_for_magic0_run(struct tdescr *td,
> +						  siginfo_t *si, ucontext_t *uc)
> +{
> +	size_t resv_sz, need_sz;
> +	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 for the badly sized terminator. */
> +	need_sz = HDR_SZ;

Nit: do we need the resv_sz and need_sz variables here?

> +	head = get_starting_head(shead, need_sz, resv_sz, NULL);
> +	if (head) {

Perhaps we could fail immediately rather than relying on timeout here?

Probably not a huge deal though.

> +		head->magic = 0;
> +		head->size = HDR_SZ;
> +
> +		ASSERT_BAD_CONTEXT(&sf.uc);
> +		fake_sigreturn(&sf, sizeof(sf), 0);
> +	}
> +
> +	return 1;
> +}
> +
> +struct tdescr tde = {
> +		.name = "FAKE_SIGRETURN_BAD_SIZE_FOR_TERMINATOR",
> +		.descr = "Trigger a sigreturn using non-zero size terminator",
> +		.sig_ok = SIGSEGV,
> +		.timeout = 3,
> +		.run = fake_sigreturn_bad_size_for_magic0_run,
> +};

Either way,

Reviewed-by: Dave Martin <[email-masked]>

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