[patch 00/10] (resend) mount ownership and unprivileged mount syscall

Miklos Szeredi
2007-04-12T16:47:33Z

This patchset adds support for keeping mount ownership information in
the kernel, and allow unprivileged mount(2) and umount(2) in certain
cases.

This can be useful for the following reasons:

- mount(8) can store ownership ("user=XY" option) in the kernel
instead, or in addition to storing it in /etc/mtab. For example if
private namespaces are used with mount propagations /etc/mtab
becomes unworkable, but using /proc/mounts works fine

- fuse won't need a special suid-root mount/umount utility. Plain
umount(8) can easily be made to work with unprivileged fuse mounts

- users can use bind mounts without having to pre-configure them in
/etc/fstab

Unprivileged mounts are restricted to private namespaces created with
a special clone flag.

Changes from the previous submission:

- add namespace flag for allowing user mounts
- add clone flag to set above namespace flag
- make max number of user mounts default to 1024, since now the
namespace flag will prevent user mounts by default

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