[PATCH] s390: rt_sigreturn fix

Check return code of do_sigaltstack and force a SIGSEGV if it is -EFAULT.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NCedric Le Goater <clg@fr.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/s390/kernel/compat_signal.c

@@ -467,8 +467,6 @@ asmlinkage long sys32_rt_sigreturn(struct pt_regs *regs)
 	if (err)
 		goto badframe; 
 
-	/* It is more difficult to avoid calling this function than to
-	   call it and ignore errors.  */
 	set_fs (KERNEL_DS);
 	do_sigaltstack((stack_t __user *)&st, NULL, regs->gprs[15]);
 	set_fs (old_fs);

arch/s390/kernel/signal.c

@@ -254,9 +254,9 @@ asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 	if (restore_sigregs(regs, &frame->uc.uc_mcontext))
 		goto badframe;
 
-	/* It is more difficult to avoid calling this function than to
-	   call it and ignore errors.  */
-	do_sigaltstack(&frame->uc.uc_stack, NULL, regs->gprs[15]);
+	if (do_sigaltstack(&frame->uc.uc_stack, NULL,
+			   regs->gprs[15]) == -EFAULT)
+		goto badframe;
 	return regs->gprs[2];
 
 badframe: