Merge tag 'time-namespace-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull time namespace updates from Christian Brauner:
 "When time namespaces were introduced we missed to virtualize the
  'btime' field in /proc/stat. This confuses tasks which are in another
  time namespace with a virtualized boottime which is common in some
  container workloads. This contains Michael's series to fix 'btime'
  which Thomas asked me to take through my tree.

  To fix 'btime' virtualization we simply subtract the offset of the
  time namespace's boottime from btime before printing the stats. Note
  that since start_boottime of processes are seconds since boottime and
  the boottime stamp is now shifted according to the time namespace's
  offset, the offset of the time namespace also needs to be applied
  before the process stats are given to userspace. This avoids that
  processes shown by tools such as 'ps' appear as time travelers in the
  corresponding time namespace.

  Selftests are included to verify that btime virtualization in
  /proc/stat works as expected"

* tag 'time-namespace-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  namespace: make timens_on_fork() return nothing
  selftests/timens: added selftest for /proc/stat btime
  fs/proc: apply the time namespace offset to /proc/stat btime
  timens: additional helper functions for boottime offset handling

2 files changed, 3 insertions, 10 deletions

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 12dd41b39a7f..e2e6c5dc433f 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -153,7 +153,6 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 	struct nsproxy *old_ns = tsk->nsproxy;
 	struct user_namespace *user_ns = task_cred_xxx(tsk, user_ns);
 	struct nsproxy *new_ns;
-	int ret;
 
 	if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
 			      CLONE_NEWPID | CLONE_NEWNET |
@@ -180,11 +179,7 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 	if (IS_ERR(new_ns))
 		return  PTR_ERR(new_ns);
 
-	ret = timens_on_fork(new_ns, tsk);
-	if (ret) {
-		free_nsproxy(new_ns);
-		return ret;
-	}
+	timens_on_fork(new_ns, tsk);
 
 	tsk->nsproxy = new_ns;
 	return 0;
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index afc65e6be33e..e0f9509b17c3 100644
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -308,22 +308,20 @@ static int timens_install(struct nsset *nsset, struct ns_common *new)
 	return 0;
 }
 
-int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
+void timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
 {
 	struct ns_common *nsc = &nsproxy->time_ns_for_children->ns;
 	struct time_namespace *ns = to_time_ns(nsc);
 
 	/* create_new_namespaces() already incremented the ref counter */
 	if (nsproxy->time_ns == nsproxy->time_ns_for_children)
-		return 0;
+		return;
 
 	get_time_ns(ns);
 	put_time_ns(nsproxy->time_ns);
 	nsproxy->time_ns = ns;
 
 	timens_commit(tsk, ns);
-
-	return 0;
 }
 
 static struct user_namespace *timens_owner(struct ns_common *ns)