kernel/linux.git/include/linux/mount.h, branch v3.13-rc5

RCU'd vfsmounts

2013-11-09T05:16:19+00:00

* RCU-delayed freeing of vfsmounts * vfsmount_lock replaced with a seqlock (mount_lock) * sequence number from mount_lock is stored in nameidata->m_seq and used when we exit RCU mode * new vfsmount flag - MNT_SYNC_UMOUNT. Set by umount_tree() when its caller knows that vfsmount will have no surviving references. * synchronize_rcu() done between unlocking namespace_sem in namespace_unlock() and doing pending mntput(). * new helper: legitimize_mnt(mnt, seq). Checks the mount_lock sequence number against seq, then grabs reference to mnt. Then it rechecks mount_lock again to close the race and either returns success or drops the reference it has acquired. The subtle point is that in case of MNT_SYNC_UMOUNT we can simply decrement the refcount and sod off - aforementioned synchronize_rcu() makes sure that final mntput() won't come until we leave RCU mode. We need that, since we don't want to end up with some lazy pathwalk racing with umount() and stealing the final mntput() from it - caller of umount() may expect it to return only once the fs is shut down and we don't want to break that. In other cases (i.e. with MNT_SYNC_UMOUNT absent) we have to do full-blown mntput() in case of mount_lock sequence number mismatch happening just as we'd grabbed the reference, but in those cases we won't be stealing the final mntput() from anything that would care. * mntput_no_expire() doesn't lock anything on the fast path now. Incidentally, SMP and UP cases are handled the same way - no ifdefs there. * normal pathname resolution does *not* do any writes to mount_lock. It does, of course, bump the refcounts of vfsmount and dentry in the very end, but that's it. Signed-off-by: Al Viro

vfs: Lock in place mounts from more privileged users

2013-07-24T16:14:46+00:00

When creating a less privileged mount namespace or propogating mounts from a more privileged to a less privileged mount namespace lock the submounts so they may not be unmounted individually in the child mount namespace revealing what is under them. This enforces the reasonable expectation that it is not possible to see under a mount point. Most of the time mounts are on empty directories and revealing that does not matter, however I have seen an occassionaly sloppy configuration where there were interesting things concealed under a mount point that probably should not be revealed. Expirable submounts are not locked because they will eventually unmount automatically so whatever is under them already needs to be safe for unprivileged users to access. From a practical standpoint these restrictions do not appear to be significant for unprivileged users of the mount namespace. Recursive bind mounts and pivot_root continues to work, and mounts that are created in a mount namespace may be unmounted there. All of which means that the common idiom of keeping a directory of interesting files and using pivot_root to throw everything else away continues to work just fine. Acked-by: Serge Hallyn Acked-by: Andy Lutomirski Signed-off-by: "Eric W. Biederman"

vfs: Add a mount flag to lock read only bind mounts

2013-03-27T14:50:04+00:00

When a read-only bind mount is copied from mount namespace in a higher privileged user namespace to a mount namespace in a lesser privileged user namespace, it should not be possible to remove the the read-only restriction. Add a MNT_LOCK_READONLY mount flag to indicate that a mount must remain read-only. CC: stable@vger.kernel.org Acked-by: Serge Hallyn Signed-off-by: "Eric W. Biederman"

vfs: move fsnotify junk to struct mount

2012-01-04T03:57:12+00:00

Signed-off-by: Al Viro

vfs: move mnt_devname

2012-01-04T03:57:11+00:00

Signed-off-by: Al Viro

vfs: move mnt_list to struct mount

2012-01-04T03:57:11+00:00

Signed-off-by: Al Viro

vfs: move the rest of int fields to struct mount

2012-01-04T03:57:10+00:00

Signed-off-by: Al Viro

vfs: mnt_id/mnt_group_id moved

2012-01-04T03:57:10+00:00

Signed-off-by: Al Viro

vfs: mnt_ns moved to struct mount

2012-01-04T03:57:09+00:00

Signed-off-by: Al Viro

vfs: take mnt_share/mnt_slave/mnt_slave_list and mnt_expire to struct mount

2012-01-04T03:57:08+00:00

Signed-off-by: Al Viro