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Commit a48a7042 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/vdso: Use ->fault() instead of remap_pfn_range() for the vvar mapping 



This is IMO much less ugly, and it also opens the door to
disallowing unprivileged userspace HPET access on systems with
usable TSCs.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/c19c2909e5ee3c3d8742f916586676bb7c40345f.1451446564.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 05ef76b2

arch/x86/entry/vdso/vma.c

+57 −40
Original line number Diff line number Diff line
@@ -102,18 +102,69 @@ static const struct vm_special_mapping text_mapping = { 
	.fault = vdso_fault,

};



static int vvar_fault(const struct vm_special_mapping *sm,

		      struct vm_area_struct *vma, struct vm_fault *vmf)

{

	const struct vdso_image *image = vma->vm_mm->context.vdso_image;

	long sym_offset;

	int ret = -EFAULT;



	if (!image)

		return VM_FAULT_SIGBUS;



	sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) +

		image->sym_vvar_start;



	/*

	 * Sanity check: a symbol offset of zero means that the page

	 * does not exist for this vdso image, not that the page is at

	 * offset zero relative to the text mapping.  This should be

	 * impossible here, because sym_offset should only be zero for

	 * the page past the end of the vvar mapping.

	 */

	if (sym_offset == 0)

		return VM_FAULT_SIGBUS;



	if (sym_offset == image->sym_vvar_page) {

		ret = vm_insert_pfn(vma, (unsigned long)vmf->virtual_address,

				    __pa_symbol(&__vvar_page) >> PAGE_SHIFT);

	} else if (sym_offset == image->sym_hpet_page) {

#ifdef CONFIG_HPET_TIMER

		if (hpet_address) {

			ret = vm_insert_pfn_prot(

				vma,

				(unsigned long)vmf->virtual_address,

				hpet_address >> PAGE_SHIFT,

				pgprot_noncached(PAGE_READONLY));

		}

#endif

	} else if (sym_offset == image->sym_pvclock_page) {

		struct pvclock_vsyscall_time_info *pvti =

			pvclock_pvti_cpu0_va();

		if (pvti) {

			ret = vm_insert_pfn(

				vma,

				(unsigned long)vmf->virtual_address,

				__pa(pvti) >> PAGE_SHIFT);

		}

	}



	if (ret == 0 || ret == -EBUSY)

		return VM_FAULT_NOPAGE;



	return VM_FAULT_SIGBUS;

}



static int map_vdso(const struct vdso_image *image, bool calculate_addr)

{

	struct mm_struct *mm = current->mm;

	struct vm_area_struct *vma;

	unsigned long addr, text_start;

	int ret = 0;

	static struct page *no_pages[] = {NULL};

	static struct vm_special_mapping vvar_mapping = {

	static const struct vm_special_mapping vvar_mapping = {

		.name = "[vvar]",

		.pages = no_pages,

		.fault = vvar_fault,

	};

	struct pvclock_vsyscall_time_info *pvti;



	if (calculate_addr) {

		addr = vdso_addr(current->mm->start_stack,
@@ -153,7 +204,8 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr) 
	vma = _install_special_mapping(mm,

				       addr,

				       -image->sym_vvar_start,

				       VM_READ|VM_MAYREAD,

				       VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|

				       VM_PFNMAP,

				       &vvar_mapping);



	if (IS_ERR(vma)) {
@@ -161,41 +213,6 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr) 
		goto up_fail;

	}



	if (image->sym_vvar_page)

		ret = remap_pfn_range(vma,

				      text_start + image->sym_vvar_page,

				      __pa_symbol(&__vvar_page) >> PAGE_SHIFT,

				      PAGE_SIZE,

				      PAGE_READONLY);



	if (ret)

		goto up_fail;



#ifdef CONFIG_HPET_TIMER

	if (hpet_address && image->sym_hpet_page) {

		ret = io_remap_pfn_range(vma,

			text_start + image->sym_hpet_page,

			hpet_address >> PAGE_SHIFT,

			PAGE_SIZE,

			pgprot_noncached(PAGE_READONLY));



		if (ret)

			goto up_fail;

	}

#endif



	pvti = pvclock_pvti_cpu0_va();

	if (pvti && image->sym_pvclock_page) {

		ret = remap_pfn_range(vma,

				      text_start + image->sym_pvclock_page,

				      __pa(pvti) >> PAGE_SHIFT,

				      PAGE_SIZE,

				      PAGE_READONLY);



		if (ret)

			goto up_fail;

	}



up_fail:

	if (ret)

		current->mm->context.vdso = NULL;