Messages in this thread Patch in this message |  | | From | Andrei Vagin <> | Subject | [PATCH 4/5] arm64/vdso: Handle faults on timens page | Date | Tue, 4 Feb 2020 09:59:12 -0800 |
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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.
Signed-off-by: Andrei Vagin <avagin@gmail.com> --- arch/arm64/kernel/vdso.c | 55 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 51 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c index bc93e26ae485..2e553468b183 100644 --- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -23,6 +23,7 @@ #include <vdso/datapage.h> #include <vdso/helpers.h> #include <vdso/vsyscall.h> +#include <linux/time_namespace.h> #include <asm/cacheflush.h> #include <asm/signal32.h> @@ -171,15 +172,61 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) up_write(&mm->mmap_sem); 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; + 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; + default: + return VM_FAULT_SIGBUS; + } + + return vmf_insert_pfn(vma, vmf->address, pfn); } static int __setup_additional_pages(enum arch_vdso_type arch_index, -- 2.24.1
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