From fc9b65e3d7703e6d63875b0b233bbe26a4a513ba Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Fri, 5 Dec 2014 18:01:11 -0600 Subject: 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 Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman --- include/linux/user_namespace.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include') diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index 14105c26a836..648cf88c5d6d 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -59,6 +59,7 @@ extern struct seq_operations proc_projid_seq_operations; extern ssize_t proc_uid_map_write(struct file *, const char __user *, size_t, loff_t *); extern ssize_t proc_gid_map_write(struct file *, const char __user *, size_t, loff_t *); extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, loff_t *); +extern bool userns_may_setgroups(const struct user_namespace *ns); #else static inline struct user_namespace *get_user_ns(struct user_namespace *ns) @@ -83,6 +84,10 @@ static inline void put_user_ns(struct user_namespace *ns) { } +static inline bool userns_may_setgroups(const struct user_namespace *ns) +{ + return true; +} #endif void update_mnt_policy(struct user_namespace *userns); -- cgit v1.2.3