sh64: fix altstack switching on sigreturn

incidentally, declaring a local variable as __user (!) to make
sparse STFU is really sick.  Especially since sparse had been
100% right - it *is* a bug.

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

1 files changed, 2 insertions, 4 deletions

diff --git a/arch/sh/kernel/signal_64.c b/arch/sh/kernel/signal_64.c
index 23853814bd17..d867cd95a622 100644
--- a/arch/sh/kernel/signal_64.c
+++ b/arch/sh/kernel/signal_64.c
@@ -347,7 +347,6 @@ asmlinkage int sys_rt_sigreturn(unsigned long r2, unsigned long r3,
 {
         struct rt_sigframe __user *frame = (struct rt_sigframe __user *) (long) REF_REG_SP;
         sigset_t set;
-        stack_t __user st;
         long long ret;
 
         /* Always make any pending restarted system calls return -EINTR */
@@ -365,11 +364,10 @@ asmlinkage int sys_rt_sigreturn(unsigned long r2, unsigned long r3,
                 goto badframe;
         regs->pc -= 4;
 
-        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, REF_REG_SP);
+        if (do_sigaltstack(&frame->uc.uc_stack, NULL, REF_REG_SP) == -EFAULT)
+                goto badframe;
 
         return (int) ret;