[PATCH review 0/4] Loopback mount escape fixes

Eric W. Biederman ebiederm at xmission.com
Thu Apr 9 19:01:15 UTC 2015

Al.  Do you want involvement in any of these patches?

If not I will move them in the direction of linux-next and Linus.  I
expect they are just interesting enough that I don't want to send them
as bug fixes during rc-late.

The feedback from the review I have recevied has been incorporated into:
     git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git for-testing

While I have energy I would like to push these things and get these issues fixed.


ebiederm at xmission.com (Eric W. Biederman) writes:

> After the last round of feedback I sat down and played with my fix
> for the fact that a strategically placed rename, ".." on bind mounts
> go up past the root of the bind mount.
> The code better handles the escaped directory returning into it's bind
> mount, and is now roughly a constant factor cost in all cases from what
> the code costs without the fix.
> So I think I have found a better tradeoff between fixing this bug and
> not slowing down path name lookups in the common case.
> These fixes are against on v4.0-rc6.
> For those who like to see everything in a single tree the code is at:
>     git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git for-testing
> Eric W. Biederman (4):
>       mnt: Track which mounts use a dentry as root.
>       vfs: Test for and handle paths that are unreachable from their mnt_root
>       vfs: Handle mounts whose parents are unreachable from their mountpoint
>       vfs: Do not allow escaping from bind mounts.
>  fs/dcache.c            |  82 +++++++++++++++++++++++++++---
>  fs/internal.h          |   2 +
>  fs/mount.h             |   6 +++
>  fs/namei.c             |  57 +++++++++++++++++----
>  fs/namespace.c         | 135 +++++++++++++++++++++++++++++++++++++++++++++++--
>  include/linux/dcache.h |  13 +++++
>  include/linux/namei.h  |   2 +
>  7 files changed, 277 insertions(+), 20 deletions(-)

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