switch_root: verify initramfs by f_type, not devno

As of linux 3.14, the initramfs device will have both major and
minor 0, causing our paranoia check to fail. Make this version agnostic
by checking the filesystem type, rather than a device number.

Signed-off-by: Dave Reisner <dreisner@archlinux.org>

diff --git a/sys-utils/switch_root.c b/sys-utils/switch_root.c
index 1222fb1b49fe74fd98b3edbaf8896338d9c1a981..dac946f8c987517d36781872048ae8bc78fb23b6 100644 (file)
--- a/sys-utils/switch_root.c
+++ b/sys-utils/switch_root.c
@@ -23,6 +23,7 @@
 #include <sys/mount.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/statfs.h>
 #include <sys/param.h>
 #include <fcntl.h>
 #include <stdio.h>
@@ -36,6 +37,7 @@
 #include "c.h"
 #include "nls.h"
 #include "closestream.h"
+#include "statfs_magic.h"
 
 #ifndef MS_MOVE
 #define MS_MOVE 8192
@@ -177,12 +179,12 @@ static int switchroot(const char *newroot)
        if (cfd >= 0) {
                pid = fork();
                if (pid <= 0) {
-                       if (fstat(cfd, &sb) == 0) {
-                               if (sb.st_dev == makedev(0, 1))
-                                       recursiveRemove(cfd);
-                               else
-                                       warn(_("old root filesystem is not an initramfs"));
-                       }
+                       struct statfs stfs;
+                       if (fstatfs(cfd, &stfs) == 0 &&
+                           (stfs.f_type == STATFS_RAMFS_MAGIC || stfs.f_type == STATFS_TMPFS_MAGIC))
+                               recursiveRemove(cfd);
+                       else
+                               warn(_("old root filesystem is not an initramfs"));
 
                        if (pid == 0)
                                exit(EXIT_SUCCESS);