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authorBallarin.Marc@gmx.de <Ballarin.Marc@gmx.de>2004-08-10 00:49:36 -0700
committerGreg KH <gregkh@suse.de>2005-04-26 21:36:59 -0700
commit4723bf98c0835bc779f627d7125417aa4f84121d (patch)
treeae4bab34f3e946dac584992a1a9ee97ae6fd6813
parente2eef6d4dc31158b812b0ee2690fec3f41b92703 (diff)
[PATCH] Update the FAQ with info about hardlink security
-rw-r--r--FAQ15
1 files changed, 14 insertions, 1 deletions
diff --git a/FAQ b/FAQ
index 28f7552ae3..45337bf635 100644
--- 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
@@ -98,6 +98,19 @@ 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