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authorSeth Forshee <seth.forshee@canonical.com>2015-09-23 22:16:04 +0200
committerEric W. Biederman <ebiederm@xmission.com>2016-06-24 17:40:31 +0200
commitd07b846f6200454c50d791796edb82660192513d (patch)
tree0addc4233c4e08fc7ca69511761bbd2c7402c1de /kernel
parentuserns: Remove the now unnecessary FS_USERNS_DEV_MOUNT flag (diff)
downloadlinux-d07b846f6200454c50d791796edb82660192513d.tar.xz
linux-d07b846f6200454c50d791796edb82660192513d.zip
fs: Limit file caps to the user namespace of the super block
Capability sets attached to files must be ignored except in the user namespaces where the mounter is privileged, i.e. s_user_ns and its descendants. Otherwise a vector exists for gaining privileges in namespaces where a user is not already privileged. Add a new helper function, current_in_user_ns(), to test whether a user namespace is the same as or a descendant of another namespace. Use this helper to determine whether a file's capability set should be applied to the caps constructed during exec. --EWB Replaced in_userns with the simpler current_in_userns. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/user_namespace.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 9bafc211930c..68f594212759 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -938,6 +938,20 @@ bool userns_may_setgroups(const struct user_namespace *ns)
return allowed;
}
+/*
+ * Returns true if @ns is the same namespace as or a descendant of
+ * @target_ns.
+ */
+bool current_in_userns(const struct user_namespace *target_ns)
+{
+ struct user_namespace *ns;
+ for (ns = current_user_ns(); ns; ns = ns->parent) {
+ if (ns == target_ns)
+ return true;
+ }
+ return false;
+}
+
static inline struct user_namespace *to_user_ns(struct ns_common *ns)
{
return container_of(ns, struct user_namespace, ns);