[PATCH 0/2] timens: Remove dependency on the vDSO

[PATCH 0/2] timens: Remove dependency on the vDSO

[Thomas Weißschuh]

Previously, missing time namespace support in the vDSO meant that time
namespaces needed to be disabled globally. This was expressed in a hard
dependency on the generic vDSO library. This also meant that architectures
without any vDSO or only a stub vDSO could not enable time namespaces.
Now that all architectures using a real vDSO are using the generic library,
that dependency is not necessary anymore.

Remove the dependency and let all architectures enable time namespaces.

Based on tip/timers/vdso.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
Thomas Weißschuh (2):
      vdso/timens: Move functions to new file
      timens: Remove dependency on the vDSO

 MAINTAINERS                      |   2 +
 include/linux/time_namespace.h   |  36 ++++-----
 init/Kconfig                     |   4 +-
 kernel/time/Makefile             |   1 +
 kernel/time/namespace.c          | 132 ++-----------------------------
 kernel/time/namespace_internal.h |  28 +++++++
 kernel/time/namespace_vdso.c     | 164 +++++++++++++++++++++++++++++++++++++++
 lib/vdso/datastore.c             |  25 ------
 8 files changed, 222 insertions(+), 170 deletions(-)
---
base-commit: 84ff7434f2386a10a8e2967e06a9415dd0ecef48
change-id: 20250908-vdso-timens-decoupling-24c0eee0c6c4

Best regards,
--  
Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>

[PATCH 1/2] vdso/timens: Move functions to new file

[Thomas Weißschuh]

As a preparation of the untangling of time namespaces and the vDSO, move
the glue functions between those subsystems into a new file.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 MAINTAINERS                      |   2 +
 include/linux/time_namespace.h   |   8 ---
 kernel/time/Makefile             |   2 +-
 kernel/time/namespace.c          | 124 ++------------------------------
 kernel/time/namespace_internal.h |  13 ++++
 kernel/time/namespace_vdso.c     | 150 +++++++++++++++++++++++++++++++++++++++
 lib/vdso/datastore.c             |  25 -------
 7 files changed, 170 insertions(+), 154 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 77fdfcb55f06..6ad74a5196d1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10768,6 +10768,7 @@ S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/vdso
 F:	include/asm-generic/vdso/vsyscall.h
 F:	include/vdso/
+F:	kernel/time/namespace_vdso.c
 F:	kernel/time/vsyscall.c
 F:	lib/vdso/
 F:	tools/testing/selftests/vDSO/
@@ -21000,6 +21001,7 @@ F:	include/trace/events/timer*
 F:	kernel/time/itimer.c
 F:	kernel/time/posix-*
 F:	kernel/time/namespace.c
+F:	kernel/time/namespace_vdso.c
 
 POWER MANAGEMENT CORE
 M:	"Rafael J. Wysocki" <rafael@kernel.org>
diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
index c514d0e5a45c..0421bf1b13d7 100644
--- a/include/linux/time_namespace.h
+++ b/include/linux/time_namespace.h
@@ -38,8 +38,6 @@ static inline struct time_namespace *to_time_ns(struct ns_common *ns)
 	return container_of(ns, struct time_namespace, ns);
 }
 void __init time_ns_init(void);
-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)
@@ -117,12 +115,6 @@ static inline void __init time_ns_init(void)
 {
 }
 
-static inline int vdso_join_timens(struct task_struct *task,
-				   struct time_namespace *ns)
-{
-	return 0;
-}
-
 static inline void timens_commit(struct task_struct *tsk,
 				 struct time_namespace *ns)
 {
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index f7d52d9543cc..662bccb3b7f9 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -29,6 +29,6 @@ endif
 obj-$(CONFIG_GENERIC_GETTIMEOFDAY)		+= vsyscall.o
 obj-$(CONFIG_DEBUG_FS)				+= timekeeping_debug.o
 obj-$(CONFIG_TEST_UDELAY)			+= test_udelay.o
-obj-$(CONFIG_TIME_NS)				+= namespace.o
+obj-$(CONFIG_TIME_NS)				+= namespace.o namespace_vdso.o
 obj-$(CONFIG_TEST_CLOCKSOURCE_WATCHDOG)		+= clocksource-wdtest.o
 obj-$(CONFIG_TIME_KUNIT_TEST)			+= time_test.o
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index 652744e00eb4..903f55a2dfb2 100644
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -19,7 +19,7 @@
 #include <linux/err.h>
 #include <linux/mm.h>
 
-#include <vdso/datapage.h>
+#include "namespace_internal.h"
 
 ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim,
 				struct timens_offsets *ns_offsets)
@@ -138,117 +138,7 @@ struct time_namespace *copy_time_ns(u64 flags,
 	return clone_time_ns(user_ns, old_ns);
 }
 
-static struct timens_offset offset_from_ts(struct timespec64 off)
-{
-	struct timens_offset ret;
-
-	ret.sec = off.tv_sec;
-	ret.nsec = off.tv_nsec;
-
-	return ret;
-}
-
-/*
- * A time namespace VVAR page has the same layout as the VVAR page which
- * contains the system wide VDSO data.
- *
- * For a normal task the VVAR pages are installed in the normal ordering:
- *     VVAR
- *     PVCLOCK
- *     HVCLOCK
- *     TIMENS   <- Not really required
- *
- * Now for a timens task the pages are installed in the following order:
- *     TIMENS
- *     PVCLOCK
- *     HVCLOCK
- *     VVAR
- *
- * The check for vdso_clock->clock_mode is in the unlikely path of
- * the seq begin magic. So for the non-timens case most of the time
- * 'seq' is even, so the branch is not taken.
- *
- * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check
- * for vdso_clock->clock_mode is a non-issue. The task is spin waiting for the
- * update to finish and for 'seq' to become even anyway.
- *
- * Timens page has vdso_clock->clock_mode set to VDSO_CLOCKMODE_TIMENS which
- * enforces the time namespace handling path.
- */
-static void timens_setup_vdso_clock_data(struct vdso_clock *vc,
-					 struct time_namespace *ns)
-{
-	struct timens_offset *offset = vc->offset;
-	struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic);
-	struct timens_offset boottime = offset_from_ts(ns->offsets.boottime);
-
-	vc->seq				= 1;
-	vc->clock_mode			= VDSO_CLOCKMODE_TIMENS;
-	offset[CLOCK_MONOTONIC]		= monotonic;
-	offset[CLOCK_MONOTONIC_RAW]	= monotonic;
-	offset[CLOCK_MONOTONIC_COARSE]	= monotonic;
-	offset[CLOCK_BOOTTIME]		= boottime;
-	offset[CLOCK_BOOTTIME_ALARM]	= boottime;
-}
-
-struct page *find_timens_vvar_page(struct vm_area_struct *vma)
-{
-	if (likely(vma->vm_mm == current->mm))
-		return current->nsproxy->time_ns->vvar_page;
-
-	/*
-	 * VM_PFNMAP | VM_IO protect .fault() handler from being called
-	 * through interfaces like /proc/$pid/mem or
-	 * process_vm_{readv,writev}() as long as there's no .access()
-	 * in special_mapping_vmops().
-	 * For more details check_vma_flags() and __access_remote_vm()
-	 */
-
-	WARN(1, "vvar_page accessed remotely");
-
-	return NULL;
-}
-
-/*
- * Protects possibly multiple offsets writers racing each other
- * and tasks entering the namespace.
- */
-static DEFINE_MUTEX(offset_lock);
-
-static void timens_set_vvar_page(struct task_struct *task,
-				struct time_namespace *ns)
-{
-	struct vdso_time_data *vdata;
-	struct vdso_clock *vc;
-	unsigned int i;
-
-	if (ns == &init_time_ns)
-		return;
-
-	/* Fast-path, taken by every task in namespace except the first. */
-	if (likely(ns->frozen_offsets))
-		return;
-
-	mutex_lock(&offset_lock);
-	/* Nothing to-do: vvar_page has been already initialized. */
-	if (ns->frozen_offsets)
-		goto out;
-
-	ns->frozen_offsets = true;
-	vdata = page_address(ns->vvar_page);
-	vc = vdata->clock_data;
-
-	for (i = 0; i < CS_BASES; i++)
-		timens_setup_vdso_clock_data(&vc[i], ns);
-
-	if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS)) {
-		for (i = 0; i < ARRAY_SIZE(vdata->aux_clock_data); i++)
-			timens_setup_vdso_clock_data(&vdata->aux_clock_data[i], ns);
-	}
-
-out:
-	mutex_unlock(&offset_lock);
-}
+DEFINE_MUTEX(timens_offset_lock);
 
 void free_time_ns(struct time_namespace *ns)
 {
@@ -298,12 +188,6 @@ static void timens_put(struct ns_common *ns)
 	put_time_ns(to_time_ns(ns));
 }
 
-void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
-{
-	timens_set_vvar_page(tsk, ns);
-	vdso_join_timens(tsk, ns);
-}
-
 static int timens_install(struct nsset *nsset, struct ns_common *new)
 {
 	struct nsproxy *nsproxy = nsset->nsproxy;
@@ -428,7 +312,7 @@ int proc_timens_set_offset(struct file *file, struct task_struct *p,
 			goto out;
 	}
 
-	mutex_lock(&offset_lock);
+	mutex_lock(&timens_offset_lock);
 	if (time_ns->frozen_offsets) {
 		err = -EACCES;
 		goto out_unlock;
@@ -453,7 +337,7 @@ int proc_timens_set_offset(struct file *file, struct task_struct *p,
 	}
 
 out_unlock:
-	mutex_unlock(&offset_lock);
+	mutex_unlock(&timens_offset_lock);
 out:
 	put_time_ns(time_ns);
 
diff --git a/kernel/time/namespace_internal.h b/kernel/time/namespace_internal.h
new file mode 100644
index 000000000000..e85da11abb4d
--- /dev/null
+++ b/kernel/time/namespace_internal.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TIME_NAMESPACE_INTERNAL_H
+#define _TIME_NAMESPACE_INTERNAL_H
+
+#include <linux/mutex.h>
+
+/*
+ * Protects possibly multiple offsets writers racing each other
+ * and tasks entering the namespace.
+ */
+extern struct mutex timens_offset_lock;
+
+#endif /* _TIME_NAMESPACE_INTERNAL_H */
diff --git a/kernel/time/namespace_vdso.c b/kernel/time/namespace_vdso.c
new file mode 100644
index 000000000000..96d07b60ebaf
--- /dev/null
+++ b/kernel/time/namespace_vdso.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Author: Andrei Vagin <avagin@openvz.org>
+ * Author: Dmitry Safonov <dima@arista.com>
+ */
+
+#include <linux/mm.h>
+#include <linux/time_namespace.h>
+#include <linux/time.h>
+#include <linux/vdso_datastore.h>
+
+#include <vdso/clocksource.h>
+#include <vdso/datapage.h>
+
+#include "namespace_internal.h"
+
+static struct timens_offset offset_from_ts(struct timespec64 off)
+{
+	struct timens_offset ret;
+
+	ret.sec = off.tv_sec;
+	ret.nsec = off.tv_nsec;
+
+	return ret;
+}
+
+/*
+ * A time namespace VVAR page has the same layout as the VVAR page which
+ * contains the system wide VDSO data.
+ *
+ * For a normal task the VVAR pages are installed in the normal ordering:
+ *     VVAR
+ *     PVCLOCK
+ *     HVCLOCK
+ *     TIMENS   <- Not really required
+ *
+ * Now for a timens task the pages are installed in the following order:
+ *     TIMENS
+ *     PVCLOCK
+ *     HVCLOCK
+ *     VVAR
+ *
+ * The check for vdso_clock->clock_mode is in the unlikely path of
+ * the seq begin magic. So for the non-timens case most of the time
+ * 'seq' is even, so the branch is not taken.
+ *
+ * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check
+ * for vdso_clock->clock_mode is a non-issue. The task is spin waiting for the
+ * update to finish and for 'seq' to become even anyway.
+ *
+ * Timens page has vdso_clock->clock_mode set to VDSO_CLOCKMODE_TIMENS which
+ * enforces the time namespace handling path.
+ */
+static void timens_setup_vdso_clock_data(struct vdso_clock *vc,
+					 struct time_namespace *ns)
+{
+	struct timens_offset *offset = vc->offset;
+	struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic);
+	struct timens_offset boottime = offset_from_ts(ns->offsets.boottime);
+
+	vc->seq				= 1;
+	vc->clock_mode			= VDSO_CLOCKMODE_TIMENS;
+	offset[CLOCK_MONOTONIC]		= monotonic;
+	offset[CLOCK_MONOTONIC_RAW]	= monotonic;
+	offset[CLOCK_MONOTONIC_COARSE]	= monotonic;
+	offset[CLOCK_BOOTTIME]		= boottime;
+	offset[CLOCK_BOOTTIME_ALARM]	= boottime;
+}
+
+struct page *find_timens_vvar_page(struct vm_area_struct *vma)
+{
+	if (likely(vma->vm_mm == current->mm))
+		return current->nsproxy->time_ns->vvar_page;
+
+	/*
+	 * VM_PFNMAP | VM_IO protect .fault() handler from being called
+	 * through interfaces like /proc/$pid/mem or
+	 * process_vm_{readv,writev}() as long as there's no .access()
+	 * in special_mapping_vmops().
+	 * For more details check_vma_flags() and __access_remote_vm()
+	 */
+
+	WARN(1, "vvar_page accessed remotely");
+
+	return NULL;
+}
+
+static void timens_set_vvar_page(struct task_struct *task,
+				struct time_namespace *ns)
+{
+	struct vdso_time_data *vdata;
+	struct vdso_clock *vc;
+	unsigned int i;
+
+	if (ns == &init_time_ns)
+		return;
+
+	/* Fast-path, taken by every task in namespace except the first. */
+	if (likely(ns->frozen_offsets))
+		return;
+
+	mutex_lock(&timens_offset_lock);
+	/* Nothing to-do: vvar_page has been already initialized. */
+	if (ns->frozen_offsets)
+		goto out;
+
+	ns->frozen_offsets = true;
+	vdata = page_address(ns->vvar_page);
+	vc = vdata->clock_data;
+
+	for (i = 0; i < CS_BASES; i++)
+		timens_setup_vdso_clock_data(&vc[i], ns);
+
+	if (IS_ENABLED(CONFIG_POSIX_AUX_CLOCKS)) {
+		for (i = 0; i < ARRAY_SIZE(vdata->aux_clock_data); i++)
+			timens_setup_vdso_clock_data(&vdata->aux_clock_data[i], ns);
+	}
+
+out:
+	mutex_unlock(&timens_offset_lock);
+}
+
+/*
+ * The vvar page layout depends on whether a task belongs to the root or
+ * non-root time namespace. Whenever a task changes its namespace, the VVAR
+ * page tables are cleared and then they will be re-faulted with a
+ * corresponding layout.
+ * See also the comment near timens_setup_vdso_clock_data() for details.
+ */
+static int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
+{
+	struct mm_struct *mm = task->mm;
+	struct vm_area_struct *vma;
+	VMA_ITERATOR(vmi, mm, 0);
+
+	mmap_read_lock(mm);
+	for_each_vma(vmi, vma) {
+		if (vma_is_special_mapping(vma, &vdso_vvar_mapping))
+			zap_vma_pages(vma);
+	}
+	mmap_read_unlock(mm);
+
+	return 0;
+}
+
+void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
+{
+	timens_set_vvar_page(tsk, ns);
+	vdso_join_timens(tsk, ns);
+}
diff --git a/lib/vdso/datastore.c b/lib/vdso/datastore.c
index faebf5b7cd6e..cf5d784a4a5a 100644
--- a/lib/vdso/datastore.c
+++ b/lib/vdso/datastore.c
@@ -132,28 +132,3 @@ struct vm_area_struct *vdso_install_vvar_mapping(struct mm_struct *mm, unsigned
 					VM_MIXEDMAP | VM_SEALED_SYSMAP,
 					&vdso_vvar_mapping);
 }
-
-#ifdef CONFIG_TIME_NS
-/*
- * The vvar page layout depends on whether a task belongs to the root or
- * non-root time namespace. Whenever a task changes its namespace, the VVAR
- * page tables are cleared and then they will be re-faulted with a
- * corresponding layout.
- * See also the comment near timens_setup_vdso_clock_data() for details.
- */
-int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
-{
-	struct mm_struct *mm = task->mm;
-	struct vm_area_struct *vma;
-	VMA_ITERATOR(vmi, mm, 0);
-
-	mmap_read_lock(mm);
-	for_each_vma(vmi, vma) {
-		if (vma_is_special_mapping(vma, &vdso_vvar_mapping))
-			zap_vma_pages(vma);
-	}
-	mmap_read_unlock(mm);
-
-	return 0;
-}
-#endif

-- 
2.53.0

[PATCH 2/2] timens: Remove dependency on the vDSO

[Thomas Weißschuh]

Previously, missing time namespace support in the vDSO meant that time
namespaces needed to be disabled globally. This was expressed in a hard
dependency on the generic vDSO library. This also meant that architectures
without any vDSO or only a stub vDSO could not enable time namespaces.
Now that all architectures using a real vDSO are using the generic library,
that dependency is not necessary anymore.

Remove the dependency and let all architectures enable time namespaces.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 include/linux/time_namespace.h   | 28 ++++++++++++++++------------
 init/Kconfig                     |  4 +++-
 kernel/time/Makefile             |  3 ++-
 kernel/time/namespace.c          |  8 ++++----
 kernel/time/namespace_internal.h | 15 +++++++++++++++
 kernel/time/namespace_vdso.c     | 14 ++++++++++++++
 6 files changed, 54 insertions(+), 18 deletions(-)

diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
index 0421bf1b13d7..c1de21a27c34 100644
--- a/include/linux/time_namespace.h
+++ b/include/linux/time_namespace.h
@@ -25,7 +25,9 @@ struct time_namespace {
 	struct ucounts		*ucounts;
 	struct ns_common	ns;
 	struct timens_offsets	offsets;
+#ifdef CONFIG_TIME_NS_VDSO
 	struct page		*vvar_page;
+#endif
 	/* If set prevents changing offsets after any task joined namespace. */
 	bool			frozen_offsets;
 } __randomize_layout;
@@ -38,7 +40,6 @@ static inline struct time_namespace *to_time_ns(struct ns_common *ns)
 	return container_of(ns, struct time_namespace, ns);
 }
 void __init time_ns_init(void);
-extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns);
 
 static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
 {
@@ -51,7 +52,6 @@ struct time_namespace *copy_time_ns(u64 flags,
 				    struct time_namespace *old_ns);
 void free_time_ns(struct time_namespace *ns);
 void timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk);
-struct page *find_timens_vvar_page(struct vm_area_struct *vma);
 
 static inline void put_time_ns(struct time_namespace *ns)
 {
@@ -115,11 +115,6 @@ static inline void __init time_ns_init(void)
 {
 }
 
-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;
@@ -146,11 +141,6 @@ static inline void timens_on_fork(struct nsproxy *nsproxy,
 	return;
 }
 
-static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)
-{
-	return NULL;
-}
-
 static inline void timens_add_monotonic(struct timespec64 *ts) { }
 static inline void timens_add_boottime(struct timespec64 *ts) { }
 
@@ -167,4 +157,18 @@ static inline ktime_t timens_ktime_to_host(clockid_t clockid, ktime_t tim)
 }
 #endif
 
+#ifdef CONFIG_TIME_NS_VDSO
+extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns);
+struct page *find_timens_vvar_page(struct vm_area_struct *vma);
+#else /* !CONFIG_TIME_NS_VDSO */
+static inline void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
+{
+}
+
+static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)
+{
+	return NULL;
+}
+#endif /* CONFIG_TIME_NS_VDSO */
+
 #endif /* _LINUX_TIMENS_H */
diff --git a/init/Kconfig b/init/Kconfig
index 444ce811ea67..5e710b03a27a 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1386,12 +1386,14 @@ config UTS_NS
 
 config TIME_NS
 	bool "TIME namespace"
-	depends on GENERIC_GETTIMEOFDAY
 	default y
 	help
 	  In this namespace boottime and monotonic clocks can be set.
 	  The time will keep going with the same pace.
 
+config TIME_NS_VDSO
+	def_bool TIME_NS && GENERIC_GETTIMEOFDAY
+
 config IPC_NS
 	bool "IPC namespace"
 	depends on (SYSVIPC || POSIX_MQUEUE)
diff --git a/kernel/time/Makefile b/kernel/time/Makefile
index 662bccb3b7f9..eaf290c972f9 100644
--- a/kernel/time/Makefile
+++ b/kernel/time/Makefile
@@ -29,6 +29,7 @@ endif
 obj-$(CONFIG_GENERIC_GETTIMEOFDAY)		+= vsyscall.o
 obj-$(CONFIG_DEBUG_FS)				+= timekeeping_debug.o
 obj-$(CONFIG_TEST_UDELAY)			+= test_udelay.o
-obj-$(CONFIG_TIME_NS)				+= namespace.o namespace_vdso.o
+obj-$(CONFIG_TIME_NS)				+= namespace.o
+obj-$(CONFIG_TIME_NS_VDSO)			+= namespace_vdso.o
 obj-$(CONFIG_TEST_CLOCKSOURCE_WATCHDOG)		+= clocksource-wdtest.o
 obj-$(CONFIG_TIME_KUNIT_TEST)			+= time_test.o
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index 903f55a2dfb2..42302cc3f3fb 100644
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -93,8 +93,8 @@ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
 	if (!ns)
 		goto fail_dec;
 
-	ns->vvar_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
-	if (!ns->vvar_page)
+	err = timens_vdso_alloc_vvar_page(ns);
+	if (err)
 		goto fail_free;
 
 	err = ns_common_init(ns);
@@ -109,7 +109,7 @@ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
 	return ns;
 
 fail_free_page:
-	__free_page(ns->vvar_page);
+	timens_vdso_free_vvar_page(ns);
 fail_free:
 	kfree(ns);
 fail_dec:
@@ -146,7 +146,7 @@ void free_time_ns(struct time_namespace *ns)
 	dec_time_namespaces(ns->ucounts);
 	put_user_ns(ns->user_ns);
 	ns_common_free(ns);
-	__free_page(ns->vvar_page);
+	timens_vdso_free_vvar_page(ns);
 	/* Concurrent nstree traversal depends on a grace period. */
 	kfree_rcu(ns, ns.ns_rcu);
 }
diff --git a/kernel/time/namespace_internal.h b/kernel/time/namespace_internal.h
index e85da11abb4d..b37ba179f43b 100644
--- a/kernel/time/namespace_internal.h
+++ b/kernel/time/namespace_internal.h
@@ -4,10 +4,25 @@
 
 #include <linux/mutex.h>
 
+struct time_namespace;
+
 /*
  * Protects possibly multiple offsets writers racing each other
  * and tasks entering the namespace.
  */
 extern struct mutex timens_offset_lock;
 
+#ifdef CONFIG_TIME_NS_VDSO
+int timens_vdso_alloc_vvar_page(struct time_namespace *ns);
+void timens_vdso_free_vvar_page(struct time_namespace *ns);
+#else /* !CONFIG_TIME_NS_VDSO */
+static inline int timens_vdso_alloc_vvar_page(struct time_namespace *ns)
+{
+	return 0;
+}
+static inline void timens_vdso_free_vvar_page(struct time_namespace *ns)
+{
+}
+#endif /* CONFIG_TIME_NS_VDSO */
+
 #endif /* _TIME_NAMESPACE_INTERNAL_H */
diff --git a/kernel/time/namespace_vdso.c b/kernel/time/namespace_vdso.c
index 96d07b60ebaf..4ab0d89ad9e0 100644
--- a/kernel/time/namespace_vdso.c
+++ b/kernel/time/namespace_vdso.c
@@ -148,3 +148,17 @@ void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
 	timens_set_vvar_page(tsk, ns);
 	vdso_join_timens(tsk, ns);
 }
+
+int timens_vdso_alloc_vvar_page(struct time_namespace *ns)
+{
+	ns->vvar_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+	if (!ns->vvar_page)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void timens_vdso_free_vvar_page(struct time_namespace *ns)
+{
+	__free_page(ns->vvar_page);
+}

-- 
2.53.0

Re: [PATCH 1/2] vdso/timens: Move functions to new file

[Thomas Gleixner]

On Mon, Mar 23 2026 at 09:07, Thomas Weißschuh wrote:
> +static void timens_set_vvar_page(struct task_struct *task,
> +				struct time_namespace *ns)
> +{
> +	struct vdso_time_data *vdata;
> +	struct vdso_clock *vc;
> +	unsigned int i;
> +
> +	if (ns == &init_time_ns)
> +		return;
> +
> +	/* Fast-path, taken by every task in namespace except the first. */
> +	if (likely(ns->frozen_offsets))
> +		return;
> +
> +	mutex_lock(&timens_offset_lock);

Please convert all the locking to guard() while at it.

Thanks,

        tglx

Re: [PATCH 1/2] vdso/timens: Move functions to new file

[Thomas Weißschuh]

On Tue, Mar 24, 2026 at 08:36:48PM +0100, Thomas Gleixner wrote:
> On Mon, Mar 23 2026 at 09:07, Thomas Weißschuh wrote:
> > +static void timens_set_vvar_page(struct task_struct *task,
> > +				struct time_namespace *ns)
> > +{
> > +	struct vdso_time_data *vdata;
> > +	struct vdso_clock *vc;
> > +	unsigned int i;
> > +
> > +	if (ns == &init_time_ns)
> > +		return;
> > +
> > +	/* Fast-path, taken by every task in namespace except the first. */
> > +	if (likely(ns->frozen_offsets))
> > +		return;
> > +
> > +	mutex_lock(&timens_offset_lock);
> 
> Please convert all the locking to guard() while at it.

I'll switch the one in timens_set_vvar_page().
proc_timens_set_offset() is not really touched in this series
and properly migrating it to guard() will also require the introduction
of __free(time_ns), which exceeds the scope of this series.

For this I'll send dedicated patches after the current series.


Thomas