diff options
Diffstat (limited to 'userns-Don-t-allow-setgroups-until-a-gid-mapping-has.patch')
| -rw-r--r-- | userns-Don-t-allow-setgroups-until-a-gid-mapping-has.patch | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/userns-Don-t-allow-setgroups-until-a-gid-mapping-has.patch b/userns-Don-t-allow-setgroups-until-a-gid-mapping-has.patch new file mode 100644 index 000000000..81217d2a5 --- /dev/null +++ b/userns-Don-t-allow-setgroups-until-a-gid-mapping-has.patch @@ -0,0 +1,98 @@ +From: "Eric W. Biederman" <ebiederm@xmission.com> +Date: Fri, 5 Dec 2014 18:01:11 -0600 +Subject: [PATCH] userns: Don't allow setgroups until a gid mapping has been + setablished + +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. + +Cc: stable@vger.kernel.org +Reviewed-by: Andy Lutomirski <luto@amacapital.net> +Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> +--- + include/linux/user_namespace.h | 5 +++++ + kernel/groups.c | 4 +++- + kernel/user_namespace.c | 14 ++++++++++++++ + 3 files changed, 22 insertions(+), 1 deletion(-) + +diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h +index e95372654f09..8d493083486a 100644 +--- a/include/linux/user_namespace.h ++++ b/include/linux/user_namespace.h +@@ -63,6 +63,7 @@ extern const 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) +@@ -87,6 +88,10 @@ static inline void put_user_ns(struct user_namespace *ns) + { + } + ++static inline bool userns_may_setgroups(const struct user_namespace *ns) ++{ ++ return true; ++} + #endif + + #endif /* _LINUX_USER_H */ +diff --git a/kernel/groups.c b/kernel/groups.c +index 02d8a251c476..664411f171b5 100644 +--- a/kernel/groups.c ++++ b/kernel/groups.c +@@ -6,6 +6,7 @@ + #include <linux/slab.h> + #include <linux/security.h> + #include <linux/syscalls.h> ++#include <linux/user_namespace.h> + #include <asm/uaccess.h> + + /* init to 2 - one for init_task, one to ensure it is never freed */ +@@ -217,7 +218,8 @@ bool may_setgroups(void) + { + struct user_namespace *user_ns = current_user_ns(); + +- return ns_capable(user_ns, CAP_SETGID); ++ return ns_capable(user_ns, CAP_SETGID) && ++ userns_may_setgroups(user_ns); + } + + /* +diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c +index b99c862a2e3f..27c8dab48c07 100644 +--- a/kernel/user_namespace.c ++++ b/kernel/user_namespace.c +@@ -843,6 +843,20 @@ 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; +-- +2.1.0 + |