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@xxxxxxx>
>> ---
>> 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@xxxxxxx>
>
Thanks
Cristian
