Messages in this thread | | | From | (Eric W. Biederman) | Date | Mon, 29 Sep 2014 16:32:22 -0700 | Subject | Re: Does MNT_LOCKED work as expected? |
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Andrey Wagin <avagin@gmail.com> writes:
> Hi All, > > I think I found a case, when MNT_LOCKED (5ff9d8a65ce8 "vfs: Lock in > place mounts from more privileged users") doesn't help to hide > overmounted parts from unprivileged users.
> The problem exists for mounts, which are not overmounted entirely. In > such cases we can open a directory from a target mount, which is not > overmounted. Then we do pivot_root to move all mounts in a temporary > directory. At the final step we deatch all mounts from the temporary > directory. After that all children mounts are umounted from the target > mount and we can use our file descriptor to open files, which have > been overmount before. > > Here is a example https://github.com/avagin/userns_vs_mntns.
I am looking at this now to make certain I am understand what you are seeing but so far it looks like lazy unmounts allow you to bypass MNT_LOCKED :(
Grumble.
Eric
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