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Filesystems and security.Filesystems and security.Posted Mar 6, 2013 20:21 UTC (Wed) by ebiederm (subscriber, #35028)Parent article: Namespaces in operation, part 6: more on user namespaces
It is true that user namespaces allow userspace to interact with more code, and thus somewhat increases the surface one has to worry about for kernel exploits.
However, most filesystems can not be mounted with just user namespace permissions. Even for the filesystems you can mount with user namespace permissions remount is not supported. So while the cited tmpfs issue could have been a problem it it occurred elsewhere in tmpfs, it was not exploitable with user namespaces.
The recent work on converting all of the filesystems for user namespace support is essentially a constructive compiler checked proof that shows that all of the uids and gids that come from userspace are properly converted into kuids. Making it safe to use existing filesystems in the presence of multiple user namespaces.
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Filesystems and security. Posted Mar 14, 2013 15:38 UTC (Thu) by impossible7 (guest, #89863) [Link]
> However, most filesystems can not be mounted with just user namespace permissions.
Are there any plans to change this? If not, is there a reason for that?
It would be nice if an ordinary user could create a user and mount namespaces and then e.g. mount an ext4 fs from a block device that they own.
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