Don't overwrite sigaction magic

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -1051,6 +1051,7 @@ static int open_pipe(int pid, struct pipe_entry *e, int *pipes_fd)
 
 static int prepare_sigactions(int pid)
 {
+	u32 type = 0;
 	int fd_sigact, ret;
 	int sig, i;
 	struct sigaction act, oact;
@@ -1061,6 +1062,12 @@ static int prepare_sigactions(int pid)
 		return 1;
 	}
 
+	ret = read(fd_sigact, &type, sizeof(type));
+	if (ret !=  sizeof(type) || type != SIGACT_MAGIC) {
+		pr_perror("%d: Bad sigactions file\n", pid);
+		return 1;
+	}
+
 	for (sig = 1; sig < SIGMAX; sig++) {
 		if (sig == SIGKILL || sig == SIGSTOP)
 			continue;

parasite.c

@@ -239,6 +239,8 @@ static int dump_sigact(parasite_args_cmd_dumpsigacts_t *args)
 		return ret;
 	}
 
+	sys_lseek(fd, MAGIC_OFFSET, SEEK_SET);
+
         for (sig = 1; sig < SIGMAX; sig++) {
 		if (sig == SIGKILL || sig == SIGSTOP)
 			continue;