[PATCH] 1GB stack size limit on PA-RISC

This patch introduces a 1GB stack size limit for stack-grows-up (ie
PA-RISC), as discussed previously.

fs/exec.c

@@ -374,7 +374,13 @@ int setup_arg_pages(struct linux_binprm *bprm)
 
 	/* Adjust bprm->p to point to the end of the strings. */
 	bprm->p = PAGE_SIZE * i - offset;
-	stack_base = STACK_TOP - current->rlim[RLIMIT_STACK].rlim_max;
+
+	/* Limit stack size to 1GB */
+	stack_base = current->rlim[RLIMIT_STACK].rlim_max;
+	if (stack_base > (1 << 30))
+		stack_base = 1 << 30;
+	stack_base = PAGE_ALIGN(STACK_TOP - stack_base);
+
 	mm->arg_start = stack_base;
 	arg_size = i << PAGE_SHIFT;