nsproxy: support CLONE_NEWTIME with setns()

So far setns() was missing time namespace support. This was partially due
to it simply not being implemented but also because vdso_join_timens()
could still fail which made switching to multiple namespaces atomically
problematic. This is now fixed so support CLONE_NEWTIME with setns()

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Andrei Vagin <avagin@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200706154912.3248030-4-christian.brauner@ubuntu.com

diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
index 824d54e..5b60313 100644 (file)
--- a/include/linux/time_namespace.h
+++ b/include/linux/time_namespace.h
@@ -33,6 +33,7 @@ extern struct time_namespace init_time_ns;
 #ifdef CONFIG_TIME_NS
 extern int vdso_join_timens(struct task_struct *task,
                            struct time_namespace *ns);
+extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns);
 
 static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
 {
@@ -96,6 +97,11 @@ static inline int vdso_join_timens(struct task_struct *task,
        return 0;
 }
 
+static inline void timens_commit(struct task_struct *tsk,
+                                struct time_namespace *ns)
+{
+}
+
 static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
 {
        return NULL;

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index cd35663..12dd41b 100644 (file)
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -262,8 +262,8 @@ void exit_task_namespaces(struct task_struct *p)
 static int check_setns_flags(unsigned long flags)
 {
        if (!flags || (flags & ~(CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
-                                CLONE_NEWNET | CLONE_NEWUSER | CLONE_NEWPID |
-                                CLONE_NEWCGROUP)))
+                                CLONE_NEWNET | CLONE_NEWTIME | CLONE_NEWUSER |
+                                CLONE_NEWPID | CLONE_NEWCGROUP)))
                return -EINVAL;
 
 #ifndef CONFIG_USER_NS
@@ -290,6 +290,10 @@ static int check_setns_flags(unsigned long flags)
        if (flags & CLONE_NEWNET)
                return -EINVAL;
 #endif
+#ifndef CONFIG_TIME_NS
+       if (flags & CLONE_NEWTIME)
+               return -EINVAL;
+#endif
 
        return 0;
 }
@@ -464,6 +468,14 @@ static int validate_nsset(struct nsset *nsset, struct pid *pid)
        }
 #endif
 
+#ifdef CONFIG_TIME_NS
+       if (flags & CLONE_NEWTIME) {
+               ret = validate_ns(nsset, &nsp->time_ns->ns);
+               if (ret)
+                       goto out;
+       }
+#endif
+
 out:
        if (pid_ns)
                put_pid_ns(pid_ns);
@@ -507,6 +519,11 @@ static void commit_nsset(struct nsset *nsset)
                exit_sem(me);
 #endif
 
+#ifdef CONFIG_TIME_NS
+       if (flags & CLONE_NEWTIME)
+               timens_commit(me, nsset->nsproxy->time_ns);
+#endif
+
        /* transfer ownership */
        switch_task_namespaces(me, nsset->nsproxy);
        nsset->nsproxy = NULL;

diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index aa7b90a..afc65e6 100644 (file)
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -280,7 +280,7 @@ static void timens_put(struct ns_common *ns)
        put_time_ns(to_time_ns(ns));
 }
 
-static void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
+void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
 {
        timens_set_vvar_page(tsk, ns);
        vdso_join_timens(tsk, ns);
@@ -298,9 +298,6 @@ static int timens_install(struct nsset *nsset, struct ns_common *new)
            !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
                return -EPERM;
 
-
-       timens_commit(current, ns);
-
        get_time_ns(ns);
        put_time_ns(nsproxy->time_ns);
        nsproxy->time_ns = ns;