Commit b1f9e876 authored by Peter Xu's avatar Peter Xu Committed by Andrew Morton
Browse files

mm/uffd: enable write protection for shmem & hugetlbfs 

We've had all the necessary changes ready for both shmem and hugetlbfs. 
Turn on all the shmem/hugetlbfs switches for userfaultfd-wp.

We can expand UFFD_API_RANGE_IOCTLS_BASIC with _UFFDIO_WRITEPROTECT too
because all existing types now support write protection mode.

Since vma_can_userfault() will be used elsewhere, move into userfaultfd_k.h.

Link: https://lkml.kernel.org/r/20220405014926.15101-1-peterx@redhat.com


Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8e165e73

fs/userfaultfd.c

+3 −18
Original line number Diff line number Diff line
@@ -1258,24 +1258,6 @@ static __always_inline int validate_range(struct mm_struct *mm, 
	return 0;

}



static inline bool vma_can_userfault(struct vm_area_struct *vma,

				     unsigned long vm_flags)

{

	/* FIXME: add WP support to hugetlbfs and shmem */

	if (vm_flags & VM_UFFD_WP) {

		if (is_vm_hugetlb_page(vma) || vma_is_shmem(vma))

			return false;

	}



	if (vm_flags & VM_UFFD_MINOR) {

		if (!(is_vm_hugetlb_page(vma) || vma_is_shmem(vma)))

			return false;

	}



	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||

	       vma_is_shmem(vma);

}



static int userfaultfd_register(struct userfaultfd_ctx *ctx,

				unsigned long arg)

{
@@ -1956,6 +1938,9 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, 
#endif

#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP

	uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;

#endif

#ifndef CONFIG_PTE_MARKER_UFFD_WP

	uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;

#endif

	uffdio_api.ioctls = UFFD_API_IOCTLS;

	ret = -EFAULT;

include/linux/userfaultfd_k.h

+20 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <linux/swap.h>

#include <linux/swapops.h>

#include <asm-generic/pgtable_uffd.h>

#include <linux/hugetlb_inline.h>



/* The set of all possible UFFD-related VM flags. */

#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR)
@@ -140,6 +141,25 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma) 
	return vma->vm_flags & __VM_UFFD_FLAGS;

}



static inline bool vma_can_userfault(struct vm_area_struct *vma,

				     unsigned long vm_flags)

{

	if (vm_flags & VM_UFFD_MINOR)

		return is_vm_hugetlb_page(vma) || vma_is_shmem(vma);



#ifndef CONFIG_PTE_MARKER_UFFD_WP

	/*

	 * If user requested uffd-wp but not enabled pte markers for

	 * uffd-wp, then shmem & hugetlbfs are not supported but only

	 * anonymous.

	 */

	if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))

		return false;

#endif

	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||

	    vma_is_shmem(vma);

}



extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);

extern void dup_userfaultfd_complete(struct list_head *);

include/uapi/linux/userfaultfd.h

+8 −2
Original line number Diff line number Diff line
@@ -33,7 +33,8 @@ 
			   UFFD_FEATURE_THREAD_ID |		\

			   UFFD_FEATURE_MINOR_HUGETLBFS |	\

			   UFFD_FEATURE_MINOR_SHMEM |		\

			   UFFD_FEATURE_EXACT_ADDRESS)

			   UFFD_FEATURE_EXACT_ADDRESS |		\

			   UFFD_FEATURE_WP_HUGETLBFS_SHMEM)

#define UFFD_API_IOCTLS				\

	((__u64)1 << _UFFDIO_REGISTER |		\

	 (__u64)1 << _UFFDIO_UNREGISTER |	\
@@ -47,7 +48,8 @@ 
#define UFFD_API_RANGE_IOCTLS_BASIC		\

	((__u64)1 << _UFFDIO_WAKE |		\

	 (__u64)1 << _UFFDIO_COPY |		\

	 (__u64)1 << _UFFDIO_CONTINUE)

	 (__u64)1 << _UFFDIO_CONTINUE |		\

	 (__u64)1 << _UFFDIO_WRITEPROTECT)



/*

 * Valid ioctl command number range with this API is from 0x00 to
@@ -194,6 +196,9 @@ struct uffdio_api { 
	 * UFFD_FEATURE_EXACT_ADDRESS indicates that the exact address of page

	 * faults would be provided and the offset within the page would not be

	 * masked.

	 *

	 * UFFD_FEATURE_WP_HUGETLBFS_SHMEM indicates that userfaultfd

	 * write-protection mode is supported on both shmem and hugetlbfs.

	 */

#define UFFD_FEATURE_PAGEFAULT_FLAG_WP		(1<<0)

#define UFFD_FEATURE_EVENT_FORK			(1<<1)
@@ -207,6 +212,7 @@ struct uffdio_api { 
#define UFFD_FEATURE_MINOR_HUGETLBFS		(1<<9)

#define UFFD_FEATURE_MINOR_SHMEM		(1<<10)

#define UFFD_FEATURE_EXACT_ADDRESS		(1<<11)

#define UFFD_FEATURE_WP_HUGETLBFS_SHMEM		(1<<12)

	__u64 features;



	__u64 ioctls;

mm/userfaultfd.c

+3 −6
Original line number Diff line number Diff line
@@ -732,15 +732,12 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, 


	err = -ENOENT;

	dst_vma = find_dst_vma(dst_mm, start, len);

	/*

	 * Make sure the vma is not shared, that the dst range is

	 * both valid and fully within a single existing vma.

	 */

	if (!dst_vma || (dst_vma->vm_flags & VM_SHARED))



	if (!dst_vma)

		goto out_unlock;

	if (!userfaultfd_wp(dst_vma))

		goto out_unlock;

	if (!vma_is_anonymous(dst_vma))

	if (!vma_can_userfault(dst_vma, dst_vma->vm_flags))

		goto out_unlock;



	if (is_vm_hugetlb_page(dst_vma)) {