If a task belongs to a time namespace then the VVAR page which contains
the system wide VDSO data is replaced with a namespace specific page
which has the same layout as the VVAR page.
Reviewed-by: Vincenzo Frascino <[email protected]>
Reviewed-by: Dmitry Safonov <[email protected]>
Signed-off-by: Andrei Vagin <[email protected]>
---
arch/arm64/kernel/vdso.c | 57 +++++++++++++++++++++++++++++++++++++---
1 file changed, 53 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 14d5b7642b62..21bdd0d74f40 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -18,6 +18,7 @@
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/slab.h>
+#include <linux/time_namespace.h>
#include <linux/timekeeper_internal.h>
#include <linux/vmalloc.h>
#include <vdso/datapage.h>
@@ -166,15 +167,63 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
mmap_write_unlock(mm);
return 0;
}
+
+static 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;
+}
+#else
+static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma)
+{
+ return NULL;
+}
#endif
static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
- if (vmf->pgoff == 0)
- return vmf_insert_pfn(vma, vmf->address,
- sym_to_pfn(vdso_data));
- return VM_FAULT_SIGBUS;
+ struct page *timens_page = find_timens_vvar_page(vma);
+ unsigned long pfn;
+
+ switch (vmf->pgoff) {
+ case VVAR_DATA_PAGE_OFFSET:
+ if (timens_page)
+ pfn = page_to_pfn(timens_page);
+ else
+ pfn = sym_to_pfn(vdso_data);
+ break;
+#ifdef CONFIG_TIME_NS
+ case VVAR_TIMENS_PAGE_OFFSET:
+ /*
+ * If a task belongs to a time namespace then a namespace
+ * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
+ * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
+ * offset.
+ * See also the comment near timens_setup_vdso_data().
+ */
+ if (!timens_page)
+ return VM_FAULT_SIGBUS;
+ pfn = sym_to_pfn(vdso_data);
+ break;
+#endif /* CONFIG_TIME_NS */
+ default:
+ return VM_FAULT_SIGBUS;
+ }
+
+ return vmf_insert_pfn(vma, vmf->address, pfn);
}
static int __setup_additional_pages(enum vdso_abi abi,
--
2.24.1