Gao feng <gaof...@cn.fujitsu.com> writes:
> Privileged user should have rights to mount/umount/move
> these even locked mount.
Hmm. This is pretty much a can't happen case, as the only exist in mount
namespaces where the global root isn't the root. How are you getting
into this situation? Using setns() ?
Why would we even care?
As implemented this patch does not handle nested user namespaces and
that really worries me at a semantic level.
We don't want to design cases where we can create containers in
containers.
Eric
> Signed-off-by: Gao feng <gaof...@cn.fujitsu.com>
> ---
> fs/namespace.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index da5c494..7097fc7 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -1297,6 +1297,11 @@ static inline bool may_mount(void)
> return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
> }
>
> +static inline bool may_mount_lock(struct mount *mnt)
> +{
> + return !(mnt->mnt.mnt_flags & MNT_LOCKED) || capable(CAP_SYS_ADMIN);
> +}
> +
> /*
> * Now umount can handle mount points as well as block devices.
> * This is important for filesystems which use unnamed block devices.
> @@ -1330,7 +1335,7 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
> goto dput_and_out;
> if (!check_mnt(mnt))
> goto dput_and_out;
> - if (mnt->mnt.mnt_flags & MNT_LOCKED)
> + if (!may_mount_lock(mnt))
> goto dput_and_out;
>
> retval = do_umount(mnt, flags);
> @@ -1768,7 +1773,8 @@ static int do_loopback(struct path *path, const char
> *old_name,
> if (!check_mnt(parent) || !check_mnt(old))
> goto out2;
>
> - if (!recurse && has_locked_children(old, old_path.dentry))
> + if (!recurse && has_locked_children(old, old_path.dentry) &&
> + !capable(CAP_SYS_ADMIN))
> goto out2;
>
> if (recurse)
> @@ -1895,7 +1901,7 @@ static int do_move_mount(struct path *path, const char
> *old_name)
> if (!check_mnt(p) || !check_mnt(old))
> goto out1;
>
> - if (old->mnt.mnt_flags & MNT_LOCKED)
> + if (!may_mount_lock(old))
> goto out1;
>
> err = -EINVAL;
> @@ -2679,7 +2685,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *,
> new_root,
> goto out4;
> if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
> goto out4;
> - if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
> + if (!may_mount_lock(new_mnt))
> goto out4;
> error = -ENOENT;
> if (d_unlinked(new.dentry))
--
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