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>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/sys-utils/switch_root.c b/sys-utils/switch_root.c
index 1222fb1b49fe74fd98b3edbaf8896338d9c1a981..975360f01d39e7545a6fce5359c9daa078f11437 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>
@@ -45,6 +46,10 @@
 #define MNT_DETACH       0x00000002    /* Just detach from the tree */
 #endif
 
+#define STATFS_RAMFS_MAGIC      0x858458f6
+#define STATFS_TMPFS_MAGIC      0x01021994
+
+
 /* remove all files/directories below dirName -- don't cross mountpoints */
 static int recursiveRemove(int fd)
 {
@@ -177,12 +182,13 @@ 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);