findmnt: allow to read (PART)UUID/LABEL from udev DB

Currently findmnt uses libmount to get filesystem properties (and
libmount uses libblkid). This works as expected, but root permissions
are required to read the tags from the devices.

It seems better to read the information from udev db and use libblkid
as fallback solution only.

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

1 files changed, 75 insertions, 14 deletions

diff --git a/misc-utils/findmnt.c b/misc-utils/findmnt.c
index 3089cce25..506fd726d 100644
--- a/misc-utils/findmnt.c
+++ b/misc-utils/findmnt.c
@@ -26,13 +26,15 @@
 #include <string.h>
 #include <termios.h>
 #ifdef HAVE_SYS_IOCTL_H
-#include <sys/ioctl.h>
+# include <sys/ioctl.h>
 #endif
 #include <assert.h>
 #include <poll.h>
 #include <sys/statvfs.h>
 #include <sys/types.h>
-
+#ifdef HAVE_LIBUDEV
+# include <libudev.h>
+#endif
 #include <libmount.h>
 
 #include "pathnames.h"
@@ -43,6 +45,7 @@
 #include "strutils.h"
 #include "xalloc.h"
 #include "optutils.h"
+#include "mangle.h"
 
 /* flags */
 enum {
@@ -146,6 +149,10 @@ static int nactions;
 /* libmount cache */
 static struct libmnt_cache *cache;
 
+#ifdef HAVE_LIBUDEV
+struct udev *udev;
+#endif
+
 static int match_func(struct libmnt_fs *fs, void *data __attribute__ ((__unused__)));
 
 
@@ -351,19 +358,71 @@ static int column_name_to_id(const char *name, size_t namesz)
 	return -1;
 }
 
+
+#ifdef HAVE_LIBUDEV
+static char *get_tag_from_udev(const char *devname, int col)
+{
+	struct udev_device *dev;
+	const char *data = NULL;
+	char *res = NULL;
+
+	if (!udev)
+		udev = udev_new();
+	if (!udev)
+		return NULL;
+
+	if (strncmp(devname, "/dev/", 5) == 0)
+		devname += 5;
+
+	dev = udev_device_new_from_subsystem_sysname(udev, "block", devname);
+	if (!dev)
+		return NULL;
+
+	switch(col) {
+	case COL_LABEL:
+		data = udev_device_get_property_value(dev, "ID_FS_LABEL_ENC");
+		break;
+	case COL_UUID:
+		data = udev_device_get_property_value(dev, "ID_FS_UUID_ENC");
+		break;
+	case COL_PARTUUID:
+		data = udev_device_get_property_value(dev, "ID_PART_ENTRY_UUID");
+		break;
+	case COL_PARTLABEL:
+		data = udev_device_get_property_value(dev, "ID_PART_ENTRY_NAME");
+		break;
+	default:
+		break;
+	}
+
+	if (data) {
+		res = xstrdup(data);
+		unhexmangle_string(res);
+	}
+
+	udev_device_unref(dev);
+	return res;
+}
+#endif /* HAVE_LIBUDEV */
+
 /* Returns LABEL or UUID */
-static const char *get_tag(struct libmnt_fs *fs, const char *tagname)
+static const char *get_tag(struct libmnt_fs *fs, const char *tagname, int col)
 {
-	const char *t, *v, *res;
+	const char *t, *v, *res = NULL;
 
 	if (!mnt_fs_get_tag(fs, &t, &v) && !strcmp(t, tagname))
 		res = v;
 	else {
-		res = mnt_fs_get_source(fs);
-		if (res)
-			res = mnt_resolve_spec(res, cache);
-		if (res)
-			res = mnt_cache_find_tag_value(cache, res, tagname);
+		const char *dev = mnt_fs_get_source(fs);
+
+		if (dev)
+			dev = mnt_resolve_spec(dev, cache);
+#ifdef HAVE_LIBUDEV
+		if (dev)
+			res = get_tag_from_udev(dev, col);
+#endif
+		if (!res)
+			res = mnt_cache_find_tag_value(cache, dev, tagname);
 	}
 
 	return res;
@@ -451,16 +510,16 @@ static const char *get_data(struct libmnt_fs *fs, int num)
 		str = mnt_fs_get_optional_fields(fs);
 		break;
 	case COL_UUID:
-		str = get_tag(fs, "UUID");
+		str = get_tag(fs, "UUID", col_id);
 		break;
 	case COL_PARTUUID:
-		str = get_tag(fs, "PARTUUID");
+		str = get_tag(fs, "PARTUUID", col_id);
 		break;
 	case COL_LABEL:
-		str = get_tag(fs, "LABEL");
+		str = get_tag(fs, "LABEL", col_id);
 		break;
 	case COL_PARTLABEL:
-		str = get_tag(fs, "PARTLABEL");
+		str = get_tag(fs, "PARTLABEL", col_id);
 		break;
 
 	case COL_MAJMIN:
@@ -1414,6 +1473,8 @@ leave:
 	mnt_free_table(tb);
 	mnt_free_cache(cache);
 	free(tabfiles);
-
+#ifdef HAVE_LIBUDEV
+	udev_unref(udev);
+#endif
 	return rc ? EXIT_FAILURE : EXIT_SUCCESS;
 }