From c7da2443d6ffa51727db09f8ef1df6aea8c7612c Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 29 Oct 2019 00:04:39 -0700 Subject: filesystem: get correct device for kernel-mounted rootfs A root filesystem mounted via the kernel command line always has a source of "/dev/root", which isn't a real device node. This makes fscrypt think this filesystem doesn't have a source device, which breaks creating login passphrase-protected directories on other filesystems: fscrypt encrypt: filesystem /: no device for mount "/": system error: cannot create filesystem link This also makes 'fscrypt status' show a blank source device: MOUNTPOINT DEVICE FILESYSTEM ENCRYPTION FSCRYPT / ext4 supported Yes To fix this case, update loadMountInfo() to map the device number to the device name via sysfs rather than use the mount source field. --- filesystem/mountpoint.go | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) (limited to 'filesystem/mountpoint.go') diff --git a/filesystem/mountpoint.go b/filesystem/mountpoint.go index 861f5b1..da6a69a 100644 --- a/filesystem/mountpoint.go +++ b/filesystem/mountpoint.go @@ -69,6 +69,18 @@ func unescapeString(str string) string { return sb.String() } +// We get the device name via the device number rather than use the mount source +// field directly. This is necessary to handle a rootfs that was mounted via +// the kernel command line, since mountinfo always shows /dev/root for that. +// This assumes that the device nodes are in the standard location. +func getDeviceName(num DeviceNumber) string { + linkPath := fmt.Sprintf("/sys/dev/block/%v", num) + if target, err := os.Readlink(linkPath); err == nil { + return fmt.Sprintf("/dev/%s", filepath.Base(target)) + } + return "" +} + // Parse one line of /proc/self/mountinfo. // // The line contains the following space-separated fields: @@ -105,9 +117,14 @@ func parseMountInfoLine(line string) *Mount { } var mnt *Mount = &Mount{} + var err error + mnt.DeviceNumber, err = newDeviceNumberFromString(fields[2]) + if err != nil { + return nil + } mnt.Path = unescapeString(fields[4]) mnt.FilesystemType = unescapeString(fields[n+1]) - mnt.Device = unescapeString(fields[n+2]) + mnt.Device = getDeviceName(mnt.DeviceNumber) return mnt } @@ -145,13 +162,8 @@ func loadMountInfo() error { // filesystems are listed in mount order. mountsByPath[mnt.Path] = mnt - var err error - mnt.Device, err = canonicalizePath(mnt.Device) - // Only use real valid devices (unlike cgroups, tmpfs, ...) - if err == nil && isDevice(mnt.Device) { + if mnt.Device != "" { mountsByDevice[mnt.Device] = append(mountsByDevice[mnt.Device], mnt) - } else { - mnt.Device = "" } } mountsInitialized = true -- cgit v1.2.3