diff mbox series

[v5,10/11] kselftest: arm64: fake_sigreturn_bad_size

Message ID 20190902112932.36129-11-cristian.marussi@arm.com (mailing list archive)
State New
Headers show
Series Add arm64/signal initial kselftest support | expand

Commit Message

Cristian Marussi Sept. 2, 2019, 11:29 a.m. UTC 
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

Comments

Dave Martin Sept. 4, 2019, 11:49 a.m. UTC | #1 
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>
Cristian Marussi Sept. 9, 2019, 6:11 p.m. UTC | #2 
On 04/09/2019 12:49, Dave Martin wrote:
> 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)?
> 

Ok
>> +	head = get_starting_head(shead, need_sz, resv_sz, &offset);

I'll also fail straight away too here on !head (no timeout) like in others

>> +	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.
> 
Ok

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

Thanks

Cristian
diff mbox series

Patch

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);
+	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;
+		/* and terminate properly */
+		write_terminator_record(GET_RESV_NEXT_HEAD(head));
+		ASSERT_BAD_CONTEXT(&sf.uc);
+		fake_sigreturn(&sf, sizeof(sf), 0);
+	}
+
+	return 1;
+}
+
+struct tdescr tde = {
+		.name = "FAKE_SIGRETURN_BAD_SIZE",
+		.descr = "Triggers a sigreturn with a overrun __reserved area",
+		.sig_ok = SIGSEGV,
+		.timeout = 3,
+		.run = fake_sigreturn_bad_size_run,
+};