linux-kernel - Re: [RFC PATCH 09/12] powerpc/kernel: Add SIG

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Date:	Wed, 15 Jul 2015 08:12:41 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	"linuxppc-dev@...abs.org" <linuxppc-dev@...abs.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>, strosake@...ux.vnet.ibm.com,
	bogdan.purcareata@...escale.com
Subject: Re: [RFC PATCH 09/12] powerpc/kernel: Add SIG_SYS support for compat tasks

On Wed, Jul 15, 2015 at 12:37 AM, Michael Ellerman <mpe@...erman.id.au> wrote:
> SIG_SYS was added in commit a0727e8ce513 "signal, x86: add SIGSYS info
> and make it synchronous."
>
> Because we use the asm-generic struct siginfo, we got support for
> SIG_SYS for free as part of that commit.
>
> However there was no compat handling added for powerpc. That means we've
> been advertising the existence of signfo._sifields._sigsys to compat
> tasks, but not actually filling in the fields correctly.
>
> Luckily it looks like no one has noticed, presumably because the only
> user of SIGSYS in the kernel is seccomp filter, which we don't support
> yet.
>
> So before we enable seccomp filter, add compat handling for SIGSYS.
>
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
> ---
>  arch/powerpc/include/asm/compat.h             | 7 +++++++
>  arch/powerpc/kernel/signal_32.c               | 5 +++++
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 4 ++++
>  3 files changed, 16 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/compat.h b/arch/powerpc/include/asm/compat.h
> index b142b8e0ed9e..4f2df589ec1d 100644
> --- a/arch/powerpc/include/asm/compat.h
> +++ b/arch/powerpc/include/asm/compat.h
> @@ -174,6 +174,13 @@ typedef struct compat_siginfo {
>                         int _band;      /* POLL_IN, POLL_OUT, POLL_MSG */
>                         int _fd;
>                 } _sigpoll;
> +
> +               /* SIGSYS */
> +               struct {
> +                       unsigned int _call_addr; /* calling insn */
> +                       int _syscall;            /* triggering system call number */
> +                       unsigned int _arch;      /* AUDIT_ARCH_* of syscall */
> +               } _sigsys;
>         } _sifields;
>  } compat_siginfo_t;
>
> diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
> index d3a831ac0f92..77f97284124e 100644
> --- a/arch/powerpc/kernel/signal_32.c
> +++ b/arch/powerpc/kernel/signal_32.c
> @@ -949,6 +949,11 @@ int copy_siginfo_to_user32(struct compat_siginfo __user *d, const siginfo_t *s)
>                 err |= __put_user(s->si_overrun, &d->si_overrun);
>                 err |= __put_user(s->si_int, &d->si_int);
>                 break;
> +       case __SI_SYS >> 16:
> +               err |= __put_user(ptr_to_compat(s->si_call_addr), &d->si_call_addr);
> +               err |= __put_user(s->si_syscall, &d->si_syscall);
> +               err |= __put_user(s->si_arch, &d->si_arch);
> +               break;
>         case __SI_RT >> 16: /* This is not generated by the kernel as of now.  */
>         case __SI_MESGQ >> 16:
>                 err |= __put_user(s->si_int, &d->si_int);
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index c5abe7fd7590..b2374c131340 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -645,6 +645,10 @@ static struct siginfo TRAP_info;
>  static volatile int TRAP_nr;
>  static void TRAP_action(int nr, siginfo_t *info, void *void_context)
>  {
> +       fprintf(stderr, "in TRAP_action\n");
> +       fprintf(stderr, "info->si_call_addr %p\n", info->si_call_addr);
> +       fprintf(stderr, "info->si_syscall %u\n", info->si_syscall);
> +       fprintf(stderr, "info->si_arch %u\n", info->si_arch);
>         memcpy(&TRAP_info, info, sizeof(TRAP_info));
>         TRAP_nr = nr;
>  }

This chunk looks like left-over debugging?

-Kees

> --
> 2.1.0
>



-- 
Kees Cook
Chrome OS Security
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