rst: Unmap restorer dyn-args memory at the end

Reported-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -1432,7 +1432,7 @@ static void *rst_mem_alloc(unsigned long size)
 	return aux;
 }
 
-static int rst_mem_remap(void *to)
+static int rst_mem_remap(struct task_restore_core_args *ta, void *to)
 {
 	if (!rst_mem_len)
 		return 0;
@@ -1446,6 +1446,8 @@ static int rst_mem_remap(void *to)
 	}
 
 	rst_mem_r = to;
+	ta->rst_mem = to;
+	ta->rst_mem_size = rst_mem_len;
 	return 0;
 }
 
@@ -2181,7 +2183,7 @@ static int sigreturn_restore(pid_t pid, CoreEntry *core)
 		goto err;
 
 	mem += vmas_len;
-	if (rst_mem_remap(mem))
+	if (rst_mem_remap(task_args, mem))
 		goto err;
 
 	task_args->timer_n = posix_timers_nr;

include/restorer.h

@@ -117,6 +117,8 @@ struct task_restore_core_args {
 	struct thread_restore_args	*thread_args;		/* array of thread arguments */
 	struct shmems			*shmems;
 	struct task_entries		*task_entries;
+	void				*rst_mem;
+	unsigned long			rst_mem_size;
 	VmaEntry			*self_vmas;
 	VmaEntry			*tgt_vmas;
 	siginfo_t			*siginfo;

pie/restorer.c

@@ -926,6 +926,8 @@ long __export_restore_task(struct task_restore_core_args *args)
 		goto core_restore_failed;
 	}
 
+	sys_munmap(args->rst_mem, args->rst_mem_size);
+
 	/*
 	 * Sigframe stack.
 	 */