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

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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
This commit is contained in:
Dmitry Safonov 2019-11-12 01:27:15 +00:00 committed by Thomas Gleixner
parent e6b28ec65b
commit 70ddf65184
3 changed files with 46 additions and 0 deletions
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27
arch/x86/entry/vdso/vma.c
View File

@ -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)
{

9
include/linux/time_namespace.h
View File

@ -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;

10
kernel/time/namespace.c
View File

@ -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;