From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Safonov Subject: [PATCHv7 25/33] x86/vdso: Zap vvar pages on switch a time namspace Date: Fri, 11 Oct 2019 02:23:33 +0100 Message-ID: <20191011012341.846266-26-dima@arista.com> References: <20191011012341.846266-1-dima@arista.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20191011012341.846266-1-dima@arista.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Dmitry Safonov , Adrian Reber , Andrei Vagin , Andy Lutomirski , Arnd Bergmann , Christian Brauner , Cyrill Gorcunov , "Eric W. Biederman" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Jeff Dike , Oleg Nesterov , Pavel Emelyanov , Shuah Khan , Thomas Gleixner , Vincenzo Frascino , containers@lists.linux-foundation.org, criu@openvz.org, linux-api@vger.kernel.org, x86@kernel.org List-Id: linux-api@vger.kernel.org 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. Co-developed-by: Andrei Vagin Signed-off-by: Andrei Vagin Signed-off-by: Dmitry Safonov --- arch/x86/entry/vdso/vma.c | 27 +++++++++++++++++++++++++++ include/linux/time_namespace.h | 3 +++ kernel/time/namespace.c | 10 ++++++++++ 3 files changed, 40 insertions(+) diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index d6cb8a16f368..57ada3e95f8d 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -50,6 +50,7 @@ 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, @@ -127,6 +128,32 @@ 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 c479cfda2c3e..dcf3dbf2836b 100644 --- a/include/linux/time_namespace.h +++ b/include/linux/time_namespace.h @@ -30,6 +30,9 @@ 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); diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c index e14cd1ca387d..0dc0742ed1ee 100644 --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -280,6 +280,7 @@ 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; @@ -290,6 +291,10 @@ 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; @@ -304,6 +309,7 @@ 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) @@ -311,6 +317,10 @@ 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; -- 2.23.0