openrisk: fix altstack switching on sigreturn

do_sigaltstack() expects _userland_ address, TYVM...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/arch/openrisc/kernel/signal.c b/arch/openrisc/kernel/signal.c
index 30110297f4f9509d6437c8f5c3e80220add6e2a9..ddedc8a77861ac4372832be8e59ce60d54d616f7 100644 (file)
--- a/arch/openrisc/kernel/signal.c
+++ b/arch/openrisc/kernel/signal.c
@@ -84,7 +84,6 @@ asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
 {
        struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
        sigset_t set;
-       stack_t st;
 
        /*
         * Since we stacked the signal on a dword boundary,
@@ -104,11 +103,10 @@ asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
        if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
                goto badframe;
 
-       if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
-               goto badframe;
        /* It is more difficult to avoid calling this function than to
           call it and ignore errors.  */
-       do_sigaltstack(&st, NULL, regs->sp);
+       if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
+               goto badframe;
 
        return regs->gpr[11];