On Wed, Aug 31, 2016 at 8:30 AM, Dmitry Safonov <[email protected]> wrote: > On 08/31/2016 06:00 PM, Andy Lutomirski wrote: >> >> On Fri, Aug 26, 2016 at 10:13 AM, Dmitry Safonov <[email protected]> >> wrote: >>> >>> Add API to change vdso blob type with arch_prctl. >>> As this is usefull only by needs of CRIU, expose >>> this interface under CONFIG_CHECKPOINT_RESTORE. >>> >>> Cc: Andy Lutomirski <[email protected]> >>> Cc: Oleg Nesterov <[email protected]> >>> Cc: Thomas Gleixner <[email protected]> >>> Cc: "H. Peter Anvin" <[email protected]> >>> Cc: Ingo Molnar <[email protected]> >>> Cc: [email protected] >>> Cc: [email protected] >>> Cc: Cyrill Gorcunov <[email protected]> >>> Cc: Pavel Emelyanov <[email protected]> >>> Signed-off-by: Dmitry Safonov <[email protected]> >>> --- >>> arch/x86/entry/vdso/vma.c | 45 >>> ++++++++++++++++++++++++++++++--------- >>> arch/x86/include/asm/vdso.h | 2 ++ >>> arch/x86/include/uapi/asm/prctl.h | 6 ++++++ >>> arch/x86/kernel/process_64.c | 25 ++++++++++++++++++++++ >>> 4 files changed, 68 insertions(+), 10 deletions(-) >>> >>> diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c >>> index 5bcb25a9e573..dad2b2d8ff03 100644 >>> --- a/arch/x86/entry/vdso/vma.c >>> +++ b/arch/x86/entry/vdso/vma.c >>> @@ -176,6 +176,16 @@ static int vvar_fault(const struct >>> vm_special_mapping *sm, >>> return VM_FAULT_SIGBUS; >>> } >>> >>> +static const struct vm_special_mapping vdso_mapping = { >>> + .name = "[vdso]", >>> + .fault = vdso_fault, >>> + .mremap = vdso_mremap, >>> +}; >>> +static const struct vm_special_mapping vvar_mapping = { >>> + .name = "[vvar]", >>> + .fault = vvar_fault, >>> +}; >>> + >>> /* >>> * Add vdso and vvar mappings to current process. >>> * @image - blob to map >>> @@ -188,16 +198,6 @@ static int map_vdso(const struct vdso_image *image, >>> unsigned long addr) >>> unsigned long text_start; >>> int ret = 0; >>> >>> - static const struct vm_special_mapping vdso_mapping = { >>> - .name = "[vdso]", >>> - .fault = vdso_fault, >>> - .mremap = vdso_mremap, >>> - }; >>> - static const struct vm_special_mapping vvar_mapping = { >>> - .name = "[vvar]", >>> - .fault = vvar_fault, >>> - }; >>> - >>> if (down_write_killable(&mm->mmap_sem)) >>> return -EINTR; >>> >>> @@ -256,6 +256,31 @@ static int map_vdso_randomized(const struct >>> vdso_image *image) >>> return map_vdso(image, addr); >>> } >>> >>> +int map_vdso_once(const struct vdso_image *image, unsigned long addr) >>> +{ >>> + struct mm_struct *mm = current->mm; >>> + struct vm_area_struct *vma; >>> + >>> + down_write(&mm->mmap_sem); >>> + /* >>> + * Check if we have already mapped vdso blob - fail to prevent >>> + * abusing from userspace install_speciall_mapping, which may >>> + * not do accounting and rlimit right. >>> + * We could search vma near context.vdso, but it's a slowpath, >>> + * so let's explicitely check all VMAs to be completely sure. >>> + */ >>> + for (vma = mm->mmap; vma; vma = vma->vm_next) { >>> + if (vma->vm_private_data == &vdso_mapping || >>> + vma->vm_private_data == &vvar_mapping) { >> >> >> Should probably also check that vm_ops == &special_mapping_vmops, >> which means that maybe there should be a: >> >> static inline bool vma_is_special_mapping(const struct vm_area_struct >> *vma, const struct vm_special_mapping &sm); > > > Oh, I remember why I didn't do it also (except header changes): > uprobes uses &special_mapping_vmops in inserted XOL area. >
That's fine. I think you should check *both* vm_ops and vm_private_data to avoid (unlikely) confusion with some other VMA. --Andy
