[PATCH] correct rule match for devices without a physical device

[elogind.git] / FAQ

diff --git a/FAQ b/FAQ
index 28f7552ae3c557b906596394f64b38f88c3bd274..bd9d63a4d50ef7e54f8b7041aeb1f8587d146b63 100644 (file)
--- a/FAQ
+++ b/FAQ
@@ -23,7 +23,7 @@ A: To quote Al Viro (Linux VFS kernel maintainer):
        - the former had stayed around for many months with maintainer
          claiming that everything works fine
        - the latter had stayed, period.
-       - the devfs maintainer/author disappeared and stoped maintaining
+       - the devfs maintainer/author disappeared and stopped maintaining
          the code.
 
 Q: But udev will not automatically load a driver if a /dev node is opened
@@ -72,10 +72,6 @@ A: udev is entirely in userspace.  If the kernel supports a greater number
 Q: Will udev support symlinks?
 A: Yes, It now does.  Multiple symlinks per device node too.
 
-Q: How will udev support changes to device permissions?
-A: On shutdown, udev will save the state of existing device permissions to
-   its database, and then used the on the next boot time.
-
 Q: How will udev handle the /dev filesystem?
 A: /dev can be a ramfs, or a backing filesystem.  udev does not care what
    kind of filesystem it runs on.
@@ -98,6 +94,19 @@ A: Technically, yes, but udev is not intended for this. Projects that do
    And don't have to be root but will get full permissions on /pendrive.
    This works even without udev if /udev/pendrive is replaced by /dev/sda1
 
+Q: Are there any security issues that I should be aware of?
+A: When using dynamic device numbers, a given pair of major/minor numbers may
+   point to different hardware over time. If a user has permission to access a
+   specific device node directly and is able to create hard links to this node,
+   he or she can do so to create a copy of the device node. When the device is
+   unplugged and udev removes the device node, the user's copy remains.
+   If the device node is later recreated with different permissions the hard 
+   link can still be used to access the device using the old permissions.
+   (The same problem exists when using PAM to change permissions on login.)
+    
+   The simplest solution is to prevent the creation of hard links by putting
+   /dev in a separate filesystem (tmpfs, ramfs, ...).
+    
 Q: I have other questions about udev, where do I ask them?
 A: The linux-hotplug-devel mailing list is the proper place for it.  The
    address for it is linux-hotplug-devel@lists.sourceforge.net