diff mbox series

[11/13] kselftest: arm64: fake_sigreturn_bad_size

Message ID 20190613111335.7645-12-cristian.marussi@arm.com
State New
Headers show
Series Add arm64/signal initial kselftest support | expand

Commit Message

Cristian Marussi June 13, 2019, 11:13 a.m. UTC
Added a simple fake_sigreturn testcase which builds a ucontext_t
with a badly sized header 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       | 40 +++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c

Comments

Dave Martin June 21, 2019, 10:36 a.m. UTC | #1
On Thu, Jun 13, 2019 at 12:13:33PM +0100, Cristian Marussi wrote:
> Added a simple fake_sigreturn testcase which builds a ucontext_t
> with a badly sized header 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       | 40 +++++++++++++++++++
>  2 files changed, 41 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 c353b7bd899d..9ad1735e0018 100644
> --- a/tools/testing/selftests/arm64/signal/testcases/.gitignore
> +++ b/tools/testing/selftests/arm64/signal/testcases/.gitignore
> @@ -8,3 +8,4 @@ mangle_pstate_invalid_mode_el3
>  mangle_pstate_ssbs_regs
>  fake_sigreturn_misaligned
>  fake_sigreturn_bad_magic
> +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..d54f79d63bf6
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
> @@ -0,0 +1,40 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (C) 2019 ARM Limited */
> +
> +#include <asm/sigcontext.h>
> +#include <ucontext.h>
> +
> +#include "test_signals_utils.h"
> +#include "testcases.h"
> +
> +struct a_sigframe sf;
> +
> +static int fake_sigreturn_bad_size_run(struct tdescr *td,
> +				       siginfo_t *si, ucontext_t *uc)
> +{
> +	struct _aarch64_ctx *head = GET_SF_RESV_HEAD(sf);
> +
> +	/* just to fill the ucontext_t with something real */
> +	if (!get_current_context(td, &sf.uc))
> +		return 1;
> +
> +	/* Tampering size to an unplausible number should cause a SEGV */
> +	head = get_terminator(head, GET_SF_RESV_SIZE(sf), NULL);
> +	if (head) {
> +		head->magic = ESR_MAGIC;

Add a comment to say why we're using this magic?

> +		head->size = GET_SF_RESV_SIZE(sf) * 2;

If we have extra_context, this might not be an invalid size, because
extra_context can be much larger than sizeof(__reserved) ... but also
we will overrun anyway, because extra_context should already be only
just large enough to accommodate the original terminator.

As with the previous test, we should probably throw away the
extra_context record (if any) and replace it with this new record.

We should check the actual boundary condition here, rather than just
testing with a giant size: we want to make the kernel detects any
overrun, however small.

We should also write a valid terminator after the new record, so
that we know the kernel is detecting the size overrun instead of
rejecting the next record because it is garbage.

> +
> +		ASSERT_BAD_CONTEXT(&sf.uc);
> +		fake_sigreturn(&sf, sizeof(sf), 16);
> +	}
> +
> +	return 1;
> +}

[...]

Cheers
---Dave
Cristian Marussi July 3, 2019, 5:46 p.m. UTC | #2
Hi

On 6/21/19 11:36 AM, Dave Martin wrote:
> On Thu, Jun 13, 2019 at 12:13:33PM +0100, Cristian Marussi wrote:
>> Added a simple fake_sigreturn testcase which builds a ucontext_t
>> with a badly sized header 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       | 40 +++++++++++++++++++
>>   2 files changed, 41 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 c353b7bd899d..9ad1735e0018 100644
>> --- a/tools/testing/selftests/arm64/signal/testcases/.gitignore
>> +++ b/tools/testing/selftests/arm64/signal/testcases/.gitignore
>> @@ -8,3 +8,4 @@ mangle_pstate_invalid_mode_el3
>>   mangle_pstate_ssbs_regs
>>   fake_sigreturn_misaligned
>>   fake_sigreturn_bad_magic
>> +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..d54f79d63bf6
>> --- /dev/null
>> +++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
>> @@ -0,0 +1,40 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/* Copyright (C) 2019 ARM Limited */
>> +
>> +#include <asm/sigcontext.h>
>> +#include <ucontext.h>
>> +
>> +#include "test_signals_utils.h"
>> +#include "testcases.h"
>> +
>> +struct a_sigframe sf;
>> +
>> +static int fake_sigreturn_bad_size_run(struct tdescr *td,
>> +				       siginfo_t *si, ucontext_t *uc)
>> +{
>> +	struct _aarch64_ctx *head = GET_SF_RESV_HEAD(sf);
>> +
>> +	/* just to fill the ucontext_t with something real */
>> +	if (!get_current_context(td, &sf.uc))
>> +		return 1;
>> +
>> +	/* Tampering size to an unplausible number should cause a SEGV */
>> +	head = get_terminator(head, GET_SF_RESV_SIZE(sf), NULL);
>> +	if (head) {
>> +		head->magic = ESR_MAGIC;
> 
> Add a comment to say why we're using this magic?
> 
>> +		head->size = GET_SF_RESV_SIZE(sf) * 2;
> 
> If we have extra_context, this might not be an invalid size, because
> extra_context can be much larger than sizeof(__reserved) ... but also
> we will overrun anyway, because extra_context should already be only
> just large enough to accommodate the original terminator.
> 
> As with the previous test, we should probably throw away the
> extra_context record (if any) and replace it with this new record.
> 
> We should check the actual boundary condition here, rather than just
> testing with a giant size: we want to make the kernel detects any
> overrun, however small.
> 
> We should also write a valid terminator after the new record, so
> that we know the kernel is detecting the size overrun instead of
> rejecting the next record because it is garbage.
> 

Fixed in V2: throwing away the extra when needed, and adding a bogus 
ESR_MAGIC with a bogus size, large enough to fit all the remaining free 
__reserved (- NULL terminator space)  + 16 bytes (to be still aligned 
and crashing out on an overrun of the least minimum size) and terminated 
with another NULL

Cristian

>> +
>> +		ASSERT_BAD_CONTEXT(&sf.uc);
>> +		fake_sigreturn(&sf, sizeof(sf), 16);
>> +	}
>> +
>> +	return 1;
>> +}
> 
> [...]
> 
> Cheers
> ---Dave
>
diff mbox series

Patch

diff --git a/tools/testing/selftests/arm64/signal/testcases/.gitignore b/tools/testing/selftests/arm64/signal/testcases/.gitignore
index c353b7bd899d..9ad1735e0018 100644
--- a/tools/testing/selftests/arm64/signal/testcases/.gitignore
+++ b/tools/testing/selftests/arm64/signal/testcases/.gitignore
@@ -8,3 +8,4 @@  mangle_pstate_invalid_mode_el3
 mangle_pstate_ssbs_regs
 fake_sigreturn_misaligned
 fake_sigreturn_bad_magic
+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..d54f79d63bf6
--- /dev/null
+++ b/tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_bad_size.c
@@ -0,0 +1,40 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 ARM Limited */
+
+#include <asm/sigcontext.h>
+#include <ucontext.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+struct a_sigframe sf;
+
+static int fake_sigreturn_bad_size_run(struct tdescr *td,
+				       siginfo_t *si, ucontext_t *uc)
+{
+	struct _aarch64_ctx *head = GET_SF_RESV_HEAD(sf);
+
+	/* just to fill the ucontext_t with something real */
+	if (!get_current_context(td, &sf.uc))
+		return 1;
+
+	/* Tampering size to an unplausible number should cause a SEGV */
+	head = get_terminator(head, GET_SF_RESV_SIZE(sf), NULL);
+	if (head) {
+		head->magic = ESR_MAGIC;
+		head->size = GET_SF_RESV_SIZE(sf) * 2;
+
+		ASSERT_BAD_CONTEXT(&sf.uc);
+		fake_sigreturn(&sf, sizeof(sf), 16);
+	}
+
+	return 1;
+}
+
+struct tdescr tde = {
+		.name = "FAKE_SIGRETURN_BAD_SIZE",
+		.descr = "Triggers a fake sigreturn with a sigframe including a bad sized head on __reserved",
+		.sig_ok = SIGSEGV,
+		.timeout = 3,
+		.run = fake_sigreturn_bad_size_run,
+};