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[PATCH] Update the FAQ with info about hardlink security
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15
FAQ
15
FAQ
@ -23,7 +23,7 @@ A: To quote Al Viro (Linux VFS kernel maintainer):
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- the former had stayed around for many months with maintainer
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- the former had stayed around for many months with maintainer
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claiming that everything works fine
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claiming that everything works fine
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- the latter had stayed, period.
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- the latter had stayed, period.
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- the devfs maintainer/author disappeared and stoped maintaining
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- the devfs maintainer/author disappeared and stopped maintaining
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the code.
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the code.
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Q: But udev will not automatically load a driver if a /dev node is opened
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Q: But udev will not automatically load a driver if a /dev node is opened
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@ -98,6 +98,19 @@ A: Technically, yes, but udev is not intended for this. Projects that do
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And don't have to be root but will get full permissions on /pendrive.
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And don't have to be root but will get full permissions on /pendrive.
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This works even without udev if /udev/pendrive is replaced by /dev/sda1
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This works even without udev if /udev/pendrive is replaced by /dev/sda1
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Q: Are there any security issues that I should be aware of?
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A: When using dynamic device numbers, a given pair of major/minor numbers may
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point to different hardware over time. If a user has permission to access a
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specific device node directly and is able to create hard links to this node,
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he or she can do so to create a copy of the device node. When the device is
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unplugged and udev removes the device node, the user's copy remains.
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If the device node is later recreated with different permissions the hard
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link can still be used to access the device using the old permissions.
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(The same problem exists when using PAM to change permissions on login.)
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The simplest solution is to prevent the creation of hard links by putting
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/dev in a separate filesystem (tmpfs, ramfs, ...).
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Q: I have other questions about udev, where do I ask them?
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Q: I have other questions about udev, where do I ask them?
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A: The linux-hotplug-devel mailing list is the proper place for it. The
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A: The linux-hotplug-devel mailing list is the proper place for it. The
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address for it is linux-hotplug-devel@lists.sourceforge.net
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address for it is linux-hotplug-devel@lists.sourceforge.net
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