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userfaultfd: wp: add UFFDIO_COPY_MODE_WP

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This allows UFFDIO_COPY to map pages write-protected.

[peterx@redhat.com: switch to VM_WARN_ON_ONCE in mfill_atomic_pte; add brackets
 around "dst_vma->vm_flags & VM_WRITE"; fix wordings in comments and
 commit messages]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-6-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli 2020-04-06 20:05:41 -07:00 committed by Linus Torvalds
parent 55adf4de30
commit 72981e0e7b
4 changed files with 36 additions and 20 deletions
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5
fs/userfaultfd.c
View file

@ -1724,11 +1724,12 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
ret = -EINVAL;
if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src)
goto out;
if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE)
if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP))
goto out;
if (mmget_not_zero(ctx->mm)) {
ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src,
uffdio_copy.len, &ctx->mmap_changing);
uffdio_copy.len, &ctx->mmap_changing,
uffdio_copy.mode);
mmput(ctx->mm);
} else {
return -ESRCH;

2
include/linux/userfaultfd_k.h
View file

@ -36,7 +36,7 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
unsigned long src_start, unsigned long len,
bool *mmap_changing);
bool *mmap_changing, __u64 mode);
extern ssize_t mfill_zeropage(struct mm_struct *dst_mm,
unsigned long dst_start,
unsigned long len,

13
include/uapi/linux/userfaultfd.h
View file

@ -203,13 +203,14 @@ struct uffdio_copy {
__u64 dst;
__u64 src;
__u64 len;
/*
* There will be a wrprotection flag later that allows to map
* pages wrprotected on the fly. And such a flag will be
* available if the wrprotection ioctl are implemented for the
* range according to the uffdio_register.ioctls.
*/
#define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0)
/*
* UFFDIO_COPY_MODE_WP will map the page write protected on
* the fly. UFFDIO_COPY_MODE_WP is available only if the
* write protected ioctl is implemented for the range
* according to the uffdio_register.ioctls.
*/
#define UFFDIO_COPY_MODE_WP ((__u64)1<<1)
__u64 mode;
/*

36
mm/userfaultfd.c
View file

@ -53,7 +53,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
struct vm_area_struct *dst_vma,
unsigned long dst_addr,
unsigned long src_addr,
struct page **pagep)
struct page **pagep,
bool wp_copy)
{
struct mem_cgroup *memcg;
pte_t _dst_pte, *dst_pte;
@ -99,9 +100,9 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false))
goto out_release;
_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
if (dst_vma->vm_flags & VM_WRITE)
_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
_dst_pte = pte_mkdirty(mk_pte(page, dst_vma->vm_page_prot));
if ((dst_vma->vm_flags & VM_WRITE) && !wp_copy)
_dst_pte = pte_mkwrite(_dst_pte);
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
if (dst_vma->vm_file) {
@ -415,7 +416,8 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
unsigned long dst_addr,
unsigned long src_addr,
struct page **page,
bool zeropage)
bool zeropage,
bool wp_copy)
{
ssize_t err;
@ -432,11 +434,13 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
if (!(dst_vma->vm_flags & VM_SHARED)) {
if (!zeropage)
err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
dst_addr, src_addr, page);
dst_addr, src_addr, page,
wp_copy);
else
err = mfill_zeropage_pte(dst_mm, dst_pmd,
dst_vma, dst_addr);
} else {
VM_WARN_ON_ONCE(wp_copy);
if (!zeropage)
err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
dst_vma, dst_addr,
@ -454,7 +458,8 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
unsigned long src_start,
unsigned long len,
bool zeropage,
bool *mmap_changing)
bool *mmap_changing,
__u64 mode)
{
struct vm_area_struct *dst_vma;
ssize_t err;
@ -462,6 +467,7 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
unsigned long src_addr, dst_addr;
long copied;
struct page *page;
bool wp_copy;
/*
* Sanitize the command parameters:
@ -507,6 +513,14 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
dst_vma->vm_flags & VM_SHARED))
goto out_unlock;
/*
* validate 'mode' now that we know the dst_vma: don't allow
* a wrprotect copy if the userfaultfd didn't register as WP.
*/
wp_copy = mode & UFFDIO_COPY_MODE_WP;
if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP))
goto out_unlock;
/*
* If this is a HUGETLB vma, pass off to appropriate routine
*/
@ -562,7 +576,7 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
BUG_ON(pmd_trans_huge(*dst_pmd));
err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
src_addr, &page, zeropage);
src_addr, &page, zeropage, wp_copy);
cond_resched();
if (unlikely(err == -ENOENT)) {
@ -609,14 +623,14 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
unsigned long src_start, unsigned long len,
bool *mmap_changing)
bool *mmap_changing, __u64 mode)
{
return __mcopy_atomic(dst_mm, dst_start, src_start, len, false,
mmap_changing);
mmap_changing, mode);
}
ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
unsigned long len, bool *mmap_changing)
{
return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing);
return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing, 0);
}