[PATCH] mdev -s: don't mistake inter-device symlinks for separate devices

[Joshua Judson Rosen]

e.g.: don't mistake the /sys/block/mtdblock*/device symlinks
(which point to the /sys/class/mtd/mtd* character devices)
as being block devices in their own right.

This was `OK' until 2013-05-13 ("mdev: use $DEVNAME in uevent...",
c3cf1e30a3022453311a7e9fe11d94c7a381640e) because the prior behaviour
of always using basename() meant that all such symlinks lead to
"/dev/device"....

Signed-off-by: Joshua Judson Rosen <jrosen at harvestai.com>
---
 util-linux/mdev.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/util-linux/mdev.c b/util-linux/mdev.c
index ca4b915..3c88213 100644
--- a/util-linux/mdev.c
+++ b/util-linux/mdev.c
@@ -559,6 +559,23 @@ static void make_device(char *device_name, char *path, int operation)
 	 * We also depend on path having writeable space after it.
 	 */
 	major = -1;
+
+	if ((path_end - path) > 7 && strncmp((path_end - 7), "/device", 7) == 0) {
+		/* Some wrapper-devices, e.g. /sys/block/mtdblock*, have
+		   a "device" symlink that points to the lower-level device--
+		   which either has already been handled separately,
+		   or will be handled separately.
+
+		   When symlink-traversal sends us down that rabbit-hole,
+		   avoid getting confused and thinking that it's actually
+		   a distinct device (e.g.: /sys/block/mtdblock1/device
+		   could trick us into thinking that /dev/mtd1 should be
+		   a block device when it shouldn't):
+		 */
+
+		return;
+	}
+
 	if (operation == OP_add) {
 		strcpy(path_end, "/dev");
 		len = open_read_close(path, path_end + 1, SCRATCH_SIZE - 1);
-- 
1.7.10.4