[PATCH v2] s390: ensure that syscall arguments are properly masked on s390

[Paul Moore]

On Mon, Jun 27, 2016 at 10:34 AM, Paul Moore <pmoore at redhat.com> wrote:
> From: Paul Moore <paul at paul-moore.com>
>
> When executing s390 code on s390x the syscall arguments are not
> properly masked, leading to some malformed audit records.
>
> Signed-off-by: Paul Moore <paul at paul-moore.com>
> ---
>  arch/s390/kernel/ptrace.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)

The only change between v2 and the original patch is the use of
is_compat_task() instead of the #ifdef, as suggested by Heiko.  Like
before, I've added this patch to the audit#next branch; I think we
have sorted all the feedback, but if any objections remain please let
me know.

> diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
> index 49b1c13..defc0dc 100644
> --- a/arch/s390/kernel/ptrace.c
> +++ b/arch/s390/kernel/ptrace.c
> @@ -822,6 +822,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
>  asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
>  {
>         long ret = 0;
> +       unsigned long mask = -1UL;
>
>         /* Do the secure computing check first. */
>         if (secure_computing()) {
> @@ -849,9 +850,12 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
>         if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
>                 trace_sys_enter(regs, regs->gprs[2]);
>
> -       audit_syscall_entry(regs->gprs[2], regs->orig_gpr2,
> -                           regs->gprs[3], regs->gprs[4],
> -                           regs->gprs[5]);
> +       if (is_compat_task())
> +               mask = 0xffffffff;
> +
> +       audit_syscall_entry(regs->gprs[2], regs->orig_gpr2 & mask,
> +                           regs->gprs[3] & mask, regs->gprs[4] & mask,
> +                           regs->gprs[5] & mask);
>  out:
>         return ret ?: regs->gprs[2];
>  }
>



-- 
paul moore
security @ redhat