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| Started by | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| First post | 2016-08-31 17:10 +0200 |
| Last post | 2016-08-31 17:50 +0200 |
| Articles | 2 — 1 participant |
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Re: [PATCHv3 3/6] x86/arch_prctl/vdso: add ARCH_MAP_VDSO_* Andy Lutomirski <luto@amacapital.net> - 2016-08-31 17:10 +0200
Re: [PATCHv3 3/6] x86/arch_prctl/vdso: add ARCH_MAP_VDSO_* Andy Lutomirski <luto@amacapital.net> - 2016-08-31 17:50 +0200
| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2016-08-31 17:10 +0200 |
| Subject | Re: [PATCHv3 3/6] x86/arch_prctl/vdso: add ARCH_MAP_VDSO_* |
| Message-ID | <scfjk-40K-43@gated-at.bofh.it> |
On Fri, Aug 26, 2016 at 10:13 AM, Dmitry Safonov <dsafonov@virtuozzo.com> 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 <luto@kernel.org>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: linux-mm@kvack.org
> Cc: x86@kernel.org
> Cc: Cyrill Gorcunov <gorcunov@openvz.org>
> Cc: Pavel Emelyanov <xemul@virtuozzo.com>
> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
> ---
> 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);
--Andy
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| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2016-08-31 17:50 +0200 |
| Message-ID | <scfW1-4eb-3@gated-at.bofh.it> |
| In reply to | #1473598 |
On Wed, Aug 31, 2016 at 8:30 AM, Dmitry Safonov <dsafonov@virtuozzo.com> wrote:
> On 08/31/2016 06:00 PM, Andy Lutomirski wrote:
>>
>> On Fri, Aug 26, 2016 at 10:13 AM, Dmitry Safonov <dsafonov@virtuozzo.com>
>> 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 <luto@kernel.org>
>>> Cc: Oleg Nesterov <oleg@redhat.com>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>>> Cc: Ingo Molnar <mingo@redhat.com>
>>> Cc: linux-mm@kvack.org
>>> Cc: x86@kernel.org
>>> Cc: Cyrill Gorcunov <gorcunov@openvz.org>
>>> Cc: Pavel Emelyanov <xemul@virtuozzo.com>
>>> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
>>> ---
>>> 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
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