lkml.org 
[lkml]   [2020]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip: timers/core] x86/vdso: Zap vvar pages when switching to a time namespace
The following commit has been merged into the timers/core branch of tip:

Commit-ID: 70ddf65184ec1e8989322f35193e4fde7377f0cc
Gitweb: https://git.kernel.org/tip/70ddf65184ec1e8989322f35193e4fde7377f0cc
Author: Dmitry Safonov <dima@arista.com>
AuthorDate: Tue, 12 Nov 2019 01:27:15
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 14 Jan 2020 12:20:59 +01:00

x86/vdso: Zap vvar pages when switching to a time namespace

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.

Co-developed-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20191112012724.250792-27-dima@arista.com


---
arch/x86/entry/vdso/vma.c | 27 +++++++++++++++++++++++++++
include/linux/time_namespace.h | 9 +++++++++
kernel/time/namespace.c | 10 ++++++++++
3 files changed, 46 insertions(+)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index d2fd8a5..c1b8496 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -51,6 +51,7 @@ void __init init_vdso_image(const struct vdso_image *image)
image->alt_len));
}

+static const struct vm_special_mapping vvar_mapping;
struct linux_binprm;

static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
@@ -128,6 +129,32 @@ static struct page *find_timens_vvar_page(struct vm_area_struct *vma)

return NULL;
}
+
+/*
+ * 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 re-faulted with a
+ * corresponding layout.
+ * See also the comment near timens_setup_vdso_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;
+
+ if (down_write_killable(&mm->mmap_sem))
+ return -EINTR;
+
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ unsigned long size = vma->vm_end - vma->vm_start;
+
+ if (vma_is_special_mapping(vma, &vvar_mapping))
+ zap_page_range(vma, vma->vm_start, size);
+ }
+
+ up_write(&mm->mmap_sem);
+ return 0;
+}
#else
static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
index 6b7767f..04a2ba8 100644
--- a/include/linux/time_namespace.h
+++ b/include/linux/time_namespace.h
@@ -31,6 +31,9 @@ struct time_namespace {
extern struct time_namespace init_time_ns;

#ifdef CONFIG_TIME_NS
+extern int vdso_join_timens(struct task_struct *task,
+ struct time_namespace *ns);
+
static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
{
kref_get(&ns->kref);
@@ -77,6 +80,12 @@ static inline ktime_t timens_ktime_to_host(clockid_t clockid, ktime_t tim)
}

#else
+static inline int vdso_join_timens(struct task_struct *task,
+ struct time_namespace *ns)
+{
+ return 0;
+}
+
static inline struct time_namespace *get_time_ns(struct time_namespace *ns)
{
return NULL;
diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
index d705c15..0732964 100644
--- a/kernel/time/namespace.c
+++ b/kernel/time/namespace.c
@@ -281,6 +281,7 @@ static void timens_put(struct ns_common *ns)
static int timens_install(struct nsproxy *nsproxy, struct ns_common *new)
{
struct time_namespace *ns = to_time_ns(new);
+ int err;

if (!current_is_single_threaded())
return -EUSERS;
@@ -291,6 +292,10 @@ static int timens_install(struct nsproxy *nsproxy, struct ns_common *new)

timens_set_vvar_page(current, ns);

+ err = vdso_join_timens(current, ns);
+ if (err)
+ return err;
+
get_time_ns(ns);
put_time_ns(nsproxy->time_ns);
nsproxy->time_ns = ns;
@@ -305,6 +310,7 @@ int 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);
+ int err;

/* create_new_namespaces() already incremented the ref counter */
if (nsproxy->time_ns == nsproxy->time_ns_for_children)
@@ -312,6 +318,10 @@ int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)

timens_set_vvar_page(tsk, ns);

+ err = vdso_join_timens(tsk, ns);
+ if (err)
+ return err;
+
get_time_ns(ns);
put_time_ns(nsproxy->time_ns);
nsproxy->time_ns = ns;
\
 
 \ /
  Last update: 2020-01-14 14:05    [W:0.307 / U:2.244 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site