diff options
author | Dmitry Safonov <dima@arista.com> | 2019-11-12 04:27:15 +0300 |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2020-01-14 14:20:59 +0300 |
commit | 70ddf65184ec1e8989322f35193e4fde7377f0cc (patch) | |
tree | 57c0c780122cece61b02950fe7c2ee6abd5457f1 | |
parent | e6b28ec65b6d433624a2c290073bc356c4fce914 (diff) | |
download | linux-70ddf65184ec1e8989322f35193e4fde7377f0cc.tar.xz |
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
-rw-r--r-- | arch/x86/entry/vdso/vma.c | 27 | ||||
-rw-r--r-- | include/linux/time_namespace.h | 9 | ||||
-rw-r--r-- | kernel/time/namespace.c | 10 |
3 files changed, 46 insertions, 0 deletions
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index d2fd8a57af7d..c1b8496b5606 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 6b7767f7df4a..04a2ba8b8a06 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 d705c15d0273..0732964803b9 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; |