diff options
author | Eric W. Biederman <ebiederm@xmission.com> | 2014-12-05 18:01:11 -0600 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-01-08 10:00:50 -0800 |
commit | f077e88fc9f0befcf0441be2fed9516881ab02ef (patch) | |
tree | 75071c6d3e84f07f38592707615ac3a9bbc8c66c /kernel/user_namespace.c | |
parent | 096b0c8d7033ef56d4c0eb13a29865a021eedea5 (diff) |
userns: Don't allow setgroups until a gid mapping has been setablished
commit 273d2c67c3e179adb1e74f403d1e9a06e3f841b5 upstream.
setgroups is unique in not needing a valid mapping before it can be called,
in the case of setgroups(0, NULL) which drops all supplemental groups.
The design of the user namespace assumes that CAP_SETGID can not actually
be used until a gid mapping is established. Therefore add a helper function
to see if the user namespace gid mapping has been established and call
that function in the setgroups permission check.
This is part of the fix for CVE-2014-8989, being able to drop groups
without privilege using user namespaces.
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/user_namespace.c')
-rw-r--r-- | kernel/user_namespace.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index e382fcdc57d6..36b432b0cb7b 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -836,6 +836,20 @@ static bool new_idmap_permitted(const struct file *file, return false; } +bool userns_may_setgroups(const struct user_namespace *ns) +{ + bool allowed; + + mutex_lock(&id_map_mutex); + /* It is not safe to use setgroups until a gid mapping in + * the user namespace has been established. + */ + allowed = ns->gid_map.nr_extents != 0; + mutex_unlock(&id_map_mutex); + + return allowed; +} + static void *userns_get(struct task_struct *task) { struct user_namespace *user_ns; |