diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2013-03-22 04:08:05 -0700 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2013-03-27 07:50:05 -0700 |
| commit | 132c94e31b8bca8ea921f9f96a57d684fa4ae0a9 (patch) | |
| tree | 52db12073a31f62301367416b2a3afec185975ef /fs/namespace.c | |
| parent | 90563b198e4c6674c63672fae1923da467215f45 (diff) | |
| download | lwn-132c94e31b8bca8ea921f9f96a57d684fa4ae0a9.tar.gz lwn-132c94e31b8bca8ea921f9f96a57d684fa4ae0a9.zip | |
vfs: Carefully propogate mounts across user namespaces
As a matter of policy MNT_READONLY should not be changable if the
original mounter had more privileges than creator of the mount
namespace.
Add the flag CL_UNPRIVILEGED to note when we are copying a mount from
a mount namespace that requires more privileges to a mount namespace
that requires fewer privileges.
When the CL_UNPRIVILEGED flag is set cause clone_mnt to set MNT_NO_REMOUNT
if any of the mnt flags that should never be changed are set.
This protects both mount propagation and the initial creation of a less
privileged mount namespace.
Cc: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 8505b5ece5de..968d4c5eae03 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -798,6 +798,10 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root, } mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; + /* Don't allow unprivileged users to change mount flags */ + if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY)) + mnt->mnt.mnt_flags |= MNT_LOCK_READONLY; + atomic_inc(&sb->s_active); mnt->mnt.mnt_sb = sb; mnt->mnt.mnt_root = dget(root); @@ -2342,7 +2346,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, /* First pass: copy the tree topology */ copy_flags = CL_COPY_ALL | CL_EXPIRE; if (user_ns != mnt_ns->user_ns) - copy_flags |= CL_SHARED_TO_SLAVE; + copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED; new = copy_tree(old, old->mnt.mnt_root, copy_flags); if (IS_ERR(new)) { up_write(&namespace_sem); |