[PATCH v2] selftests/seccomp: fix ptrace tests on powerpc
Michael Ellerman
mpe at ellerman.id.au
Sun Sep 13 17:35:29 AEST 2020
Kees Cook <keescook at chromium.org> writes:
> On Fri, Sep 11, 2020 at 03:10:12PM -0300, Thadeu Lima de Souza Cascardo wrote:
...
>> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
>> index 7a6d40286a42..0ddc0846e9c0 100644
>> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
>> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
>> @@ -1916,10 +1957,15 @@ void tracer_ptrace(struct __test_metadata *_metadata, pid_t tracee,
>> EXPECT_EQ(entry ? PTRACE_EVENTMSG_SYSCALL_ENTRY
>> : PTRACE_EVENTMSG_SYSCALL_EXIT, msg);
>>
>> - if (!entry)
>> + if (!entry && !variant)
>> return;
>>
>> - nr = get_syscall(_metadata, tracee);
>> + if (entry)
>> + nr = get_syscall(_metadata, tracee);
>> + else if (variant)
>> + nr = variant->syscall_nr;
>> + if (variant)
>> + variant->syscall_nr = nr;
>
> So, to be clear this is _only_ an issue for the ptrace side of things,
> yes? i.e. seccomp's setting of the return value will correct stick?
Yes. There's a comment which (hopefully) explains the difference here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/kernel/ptrace/ptrace.c?commit=ab29a807a7ddaa7c84d2f4cb8d29e74e33759072#n239
Which says:
static int do_seccomp(struct pt_regs *regs)
{
if (!test_thread_flag(TIF_SECCOMP))
return 0;
/*
* The ABI we present to seccomp tracers is that r3 contains
* the syscall return value and orig_gpr3 contains the first
* syscall parameter. This is different to the ptrace ABI where
* both r3 and orig_gpr3 contain the first syscall parameter.
*/
regs->gpr[3] = -ENOSYS;
cheers
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