v4.19.13 snapshot.
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
new file mode 100644
index 0000000..458acda
--- /dev/null
+++ b/mm/userfaultfd.c
@@ -0,0 +1,617 @@
+/*
+ * mm/userfaultfd.c
+ *
+ * Copyright (C) 2015 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ */
+
+#include <linux/mm.h>
+#include <linux/sched/signal.h>
+#include <linux/pagemap.h>
+#include <linux/rmap.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/userfaultfd_k.h>
+#include <linux/mmu_notifier.h>
+#include <linux/hugetlb.h>
+#include <linux/shmem_fs.h>
+#include <asm/tlbflush.h>
+#include "internal.h"
+
+static int mcopy_atomic_pte(struct mm_struct *dst_mm,
+ pmd_t *dst_pmd,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_addr,
+ unsigned long src_addr,
+ struct page **pagep)
+{
+ struct mem_cgroup *memcg;
+ pte_t _dst_pte, *dst_pte;
+ spinlock_t *ptl;
+ void *page_kaddr;
+ int ret;
+ struct page *page;
+ pgoff_t offset, max_off;
+ struct inode *inode;
+
+ if (!*pagep) {
+ ret = -ENOMEM;
+ page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
+ if (!page)
+ goto out;
+
+ page_kaddr = kmap_atomic(page);
+ ret = copy_from_user(page_kaddr,
+ (const void __user *) src_addr,
+ PAGE_SIZE);
+ kunmap_atomic(page_kaddr);
+
+ /* fallback to copy_from_user outside mmap_sem */
+ if (unlikely(ret)) {
+ ret = -ENOENT;
+ *pagep = page;
+ /* don't free the page */
+ goto out;
+ }
+ } else {
+ page = *pagep;
+ *pagep = NULL;
+ }
+
+ /*
+ * The memory barrier inside __SetPageUptodate makes sure that
+ * preceeding stores to the page contents become visible before
+ * the set_pte_at() write.
+ */
+ __SetPageUptodate(page);
+
+ ret = -ENOMEM;
+ 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_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+ if (dst_vma->vm_file) {
+ /* the shmem MAP_PRIVATE case requires checking the i_size */
+ inode = dst_vma->vm_file->f_inode;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ ret = -EFAULT;
+ if (unlikely(offset >= max_off))
+ goto out_release_uncharge_unlock;
+ }
+ ret = -EEXIST;
+ if (!pte_none(*dst_pte))
+ goto out_release_uncharge_unlock;
+
+ inc_mm_counter(dst_mm, MM_ANONPAGES);
+ page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
+ mem_cgroup_commit_charge(page, memcg, false, false);
+ lru_cache_add_active_or_unevictable(page, dst_vma);
+
+ set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
+
+ /* No need to invalidate - it was non-present before */
+ update_mmu_cache(dst_vma, dst_addr, dst_pte);
+
+ pte_unmap_unlock(dst_pte, ptl);
+ ret = 0;
+out:
+ return ret;
+out_release_uncharge_unlock:
+ pte_unmap_unlock(dst_pte, ptl);
+ mem_cgroup_cancel_charge(page, memcg, false);
+out_release:
+ put_page(page);
+ goto out;
+}
+
+static int mfill_zeropage_pte(struct mm_struct *dst_mm,
+ pmd_t *dst_pmd,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_addr)
+{
+ pte_t _dst_pte, *dst_pte;
+ spinlock_t *ptl;
+ int ret;
+ pgoff_t offset, max_off;
+ struct inode *inode;
+
+ _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
+ dst_vma->vm_page_prot));
+ dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+ if (dst_vma->vm_file) {
+ /* the shmem MAP_PRIVATE case requires checking the i_size */
+ inode = dst_vma->vm_file->f_inode;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ ret = -EFAULT;
+ if (unlikely(offset >= max_off))
+ goto out_unlock;
+ }
+ ret = -EEXIST;
+ if (!pte_none(*dst_pte))
+ goto out_unlock;
+ set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
+ /* No need to invalidate - it was non-present before */
+ update_mmu_cache(dst_vma, dst_addr, dst_pte);
+ ret = 0;
+out_unlock:
+ pte_unmap_unlock(dst_pte, ptl);
+ return ret;
+}
+
+static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
+{
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+
+ pgd = pgd_offset(mm, address);
+ p4d = p4d_alloc(mm, pgd, address);
+ if (!p4d)
+ return NULL;
+ pud = pud_alloc(mm, p4d, address);
+ if (!pud)
+ return NULL;
+ /*
+ * Note that we didn't run this because the pmd was
+ * missing, the *pmd may be already established and in
+ * turn it may also be a trans_huge_pmd.
+ */
+ return pmd_alloc(mm, pud, address);
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+/*
+ * __mcopy_atomic processing for HUGETLB vmas. Note that this routine is
+ * called with mmap_sem held, it will release mmap_sem before returning.
+ */
+static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_start,
+ unsigned long src_start,
+ unsigned long len,
+ bool zeropage)
+{
+ int vm_alloc_shared = dst_vma->vm_flags & VM_SHARED;
+ int vm_shared = dst_vma->vm_flags & VM_SHARED;
+ ssize_t err;
+ pte_t *dst_pte;
+ unsigned long src_addr, dst_addr;
+ long copied;
+ struct page *page;
+ struct hstate *h;
+ unsigned long vma_hpagesize;
+ pgoff_t idx;
+ u32 hash;
+ struct address_space *mapping;
+
+ /*
+ * There is no default zero huge page for all huge page sizes as
+ * supported by hugetlb. A PMD_SIZE huge pages may exist as used
+ * by THP. Since we can not reliably insert a zero page, this
+ * feature is not supported.
+ */
+ if (zeropage) {
+ up_read(&dst_mm->mmap_sem);
+ return -EINVAL;
+ }
+
+ src_addr = src_start;
+ dst_addr = dst_start;
+ copied = 0;
+ page = NULL;
+ vma_hpagesize = vma_kernel_pagesize(dst_vma);
+
+ /*
+ * Validate alignment based on huge page size
+ */
+ err = -EINVAL;
+ if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
+ goto out_unlock;
+
+retry:
+ /*
+ * On routine entry dst_vma is set. If we had to drop mmap_sem and
+ * retry, dst_vma will be set to NULL and we must lookup again.
+ */
+ if (!dst_vma) {
+ err = -ENOENT;
+ dst_vma = find_vma(dst_mm, dst_start);
+ if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
+ goto out_unlock;
+ /*
+ * Check the vma is registered in uffd, this is
+ * required to enforce the VM_MAYWRITE check done at
+ * uffd registration time.
+ */
+ if (!dst_vma->vm_userfaultfd_ctx.ctx)
+ goto out_unlock;
+
+ if (dst_start < dst_vma->vm_start ||
+ dst_start + len > dst_vma->vm_end)
+ goto out_unlock;
+
+ err = -EINVAL;
+ if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
+ goto out_unlock;
+
+ vm_shared = dst_vma->vm_flags & VM_SHARED;
+ }
+
+ if (WARN_ON(dst_addr & (vma_hpagesize - 1) ||
+ (len - copied) & (vma_hpagesize - 1)))
+ goto out_unlock;
+
+ /*
+ * If not shared, ensure the dst_vma has a anon_vma.
+ */
+ err = -ENOMEM;
+ if (!vm_shared) {
+ if (unlikely(anon_vma_prepare(dst_vma)))
+ goto out_unlock;
+ }
+
+ h = hstate_vma(dst_vma);
+
+ while (src_addr < src_start + len) {
+ pte_t dst_pteval;
+
+ BUG_ON(dst_addr >= dst_start + len);
+ VM_BUG_ON(dst_addr & ~huge_page_mask(h));
+
+ /*
+ * Serialize via hugetlb_fault_mutex
+ */
+ idx = linear_page_index(dst_vma, dst_addr);
+ mapping = dst_vma->vm_file->f_mapping;
+ hash = hugetlb_fault_mutex_hash(h, dst_mm, dst_vma, mapping,
+ idx, dst_addr);
+ mutex_lock(&hugetlb_fault_mutex_table[hash]);
+
+ err = -ENOMEM;
+ dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h));
+ if (!dst_pte) {
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+ goto out_unlock;
+ }
+
+ err = -EEXIST;
+ dst_pteval = huge_ptep_get(dst_pte);
+ if (!huge_pte_none(dst_pteval)) {
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+ goto out_unlock;
+ }
+
+ err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
+ dst_addr, src_addr, &page);
+
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+ vm_alloc_shared = vm_shared;
+
+ cond_resched();
+
+ if (unlikely(err == -ENOENT)) {
+ up_read(&dst_mm->mmap_sem);
+ BUG_ON(!page);
+
+ err = copy_huge_page_from_user(page,
+ (const void __user *)src_addr,
+ pages_per_huge_page(h), true);
+ if (unlikely(err)) {
+ err = -EFAULT;
+ goto out;
+ }
+ down_read(&dst_mm->mmap_sem);
+
+ dst_vma = NULL;
+ goto retry;
+ } else
+ BUG_ON(page);
+
+ if (!err) {
+ dst_addr += vma_hpagesize;
+ src_addr += vma_hpagesize;
+ copied += vma_hpagesize;
+
+ if (fatal_signal_pending(current))
+ err = -EINTR;
+ }
+ if (err)
+ break;
+ }
+
+out_unlock:
+ up_read(&dst_mm->mmap_sem);
+out:
+ if (page) {
+ /*
+ * We encountered an error and are about to free a newly
+ * allocated huge page.
+ *
+ * Reservation handling is very subtle, and is different for
+ * private and shared mappings. See the routine
+ * restore_reserve_on_error for details. Unfortunately, we
+ * can not call restore_reserve_on_error now as it would
+ * require holding mmap_sem.
+ *
+ * If a reservation for the page existed in the reservation
+ * map of a private mapping, the map was modified to indicate
+ * the reservation was consumed when the page was allocated.
+ * We clear the PagePrivate flag now so that the global
+ * reserve count will not be incremented in free_huge_page.
+ * The reservation map will still indicate the reservation
+ * was consumed and possibly prevent later page allocation.
+ * This is better than leaking a global reservation. If no
+ * reservation existed, it is still safe to clear PagePrivate
+ * as no adjustments to reservation counts were made during
+ * allocation.
+ *
+ * The reservation map for shared mappings indicates which
+ * pages have reservations. When a huge page is allocated
+ * for an address with a reservation, no change is made to
+ * the reserve map. In this case PagePrivate will be set
+ * to indicate that the global reservation count should be
+ * incremented when the page is freed. This is the desired
+ * behavior. However, when a huge page is allocated for an
+ * address without a reservation a reservation entry is added
+ * to the reservation map, and PagePrivate will not be set.
+ * When the page is freed, the global reserve count will NOT
+ * be incremented and it will appear as though we have leaked
+ * reserved page. In this case, set PagePrivate so that the
+ * global reserve count will be incremented to match the
+ * reservation map entry which was created.
+ *
+ * Note that vm_alloc_shared is based on the flags of the vma
+ * for which the page was originally allocated. dst_vma could
+ * be different or NULL on error.
+ */
+ if (vm_alloc_shared)
+ SetPagePrivate(page);
+ else
+ ClearPagePrivate(page);
+ put_page(page);
+ }
+ BUG_ON(copied < 0);
+ BUG_ON(err > 0);
+ BUG_ON(!copied && !err);
+ return copied ? copied : err;
+}
+#else /* !CONFIG_HUGETLB_PAGE */
+/* fail at build time if gcc attempts to use this */
+extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_start,
+ unsigned long src_start,
+ unsigned long len,
+ bool zeropage);
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
+ pmd_t *dst_pmd,
+ struct vm_area_struct *dst_vma,
+ unsigned long dst_addr,
+ unsigned long src_addr,
+ struct page **page,
+ bool zeropage)
+{
+ ssize_t err;
+
+ /*
+ * The normal page fault path for a shmem will invoke the
+ * fault, fill the hole in the file and COW it right away. The
+ * result generates plain anonymous memory. So when we are
+ * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
+ * generate anonymous memory directly without actually filling
+ * the hole. For the MAP_PRIVATE case the robustness check
+ * only happens in the pagetable (to verify it's still none)
+ * and not in the radix tree.
+ */
+ if (!(dst_vma->vm_flags & VM_SHARED)) {
+ if (!zeropage)
+ err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
+ dst_addr, src_addr, page);
+ else
+ err = mfill_zeropage_pte(dst_mm, dst_pmd,
+ dst_vma, dst_addr);
+ } else {
+ if (!zeropage)
+ err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
+ dst_vma, dst_addr,
+ src_addr, page);
+ else
+ err = shmem_mfill_zeropage_pte(dst_mm, dst_pmd,
+ dst_vma, dst_addr);
+ }
+
+ return err;
+}
+
+static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
+ unsigned long dst_start,
+ unsigned long src_start,
+ unsigned long len,
+ bool zeropage,
+ bool *mmap_changing)
+{
+ struct vm_area_struct *dst_vma;
+ ssize_t err;
+ pmd_t *dst_pmd;
+ unsigned long src_addr, dst_addr;
+ long copied;
+ struct page *page;
+
+ /*
+ * Sanitize the command parameters:
+ */
+ BUG_ON(dst_start & ~PAGE_MASK);
+ BUG_ON(len & ~PAGE_MASK);
+
+ /* Does the address range wrap, or is the span zero-sized? */
+ BUG_ON(src_start + len <= src_start);
+ BUG_ON(dst_start + len <= dst_start);
+
+ src_addr = src_start;
+ dst_addr = dst_start;
+ copied = 0;
+ page = NULL;
+retry:
+ down_read(&dst_mm->mmap_sem);
+
+ /*
+ * If memory mappings are changing because of non-cooperative
+ * operation (e.g. mremap) running in parallel, bail out and
+ * request the user to retry later
+ */
+ err = -EAGAIN;
+ if (mmap_changing && READ_ONCE(*mmap_changing))
+ goto out_unlock;
+
+ /*
+ * Make sure the vma is not shared, that the dst range is
+ * both valid and fully within a single existing vma.
+ */
+ err = -ENOENT;
+ dst_vma = find_vma(dst_mm, dst_start);
+ if (!dst_vma)
+ goto out_unlock;
+ /*
+ * Check the vma is registered in uffd, this is required to
+ * enforce the VM_MAYWRITE check done at uffd registration
+ * time.
+ */
+ if (!dst_vma->vm_userfaultfd_ctx.ctx)
+ goto out_unlock;
+
+ if (dst_start < dst_vma->vm_start ||
+ dst_start + len > dst_vma->vm_end)
+ goto out_unlock;
+
+ err = -EINVAL;
+ /*
+ * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
+ * it will overwrite vm_ops, so vma_is_anonymous must return false.
+ */
+ if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
+ dst_vma->vm_flags & VM_SHARED))
+ goto out_unlock;
+
+ /*
+ * If this is a HUGETLB vma, pass off to appropriate routine
+ */
+ if (is_vm_hugetlb_page(dst_vma))
+ return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
+ src_start, len, zeropage);
+
+ if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
+ goto out_unlock;
+
+ /*
+ * Ensure the dst_vma has a anon_vma or this page
+ * would get a NULL anon_vma when moved in the
+ * dst_vma.
+ */
+ err = -ENOMEM;
+ if (!(dst_vma->vm_flags & VM_SHARED) &&
+ unlikely(anon_vma_prepare(dst_vma)))
+ goto out_unlock;
+
+ while (src_addr < src_start + len) {
+ pmd_t dst_pmdval;
+
+ BUG_ON(dst_addr >= dst_start + len);
+
+ dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
+ if (unlikely(!dst_pmd)) {
+ err = -ENOMEM;
+ break;
+ }
+
+ dst_pmdval = pmd_read_atomic(dst_pmd);
+ /*
+ * If the dst_pmd is mapped as THP don't
+ * override it and just be strict.
+ */
+ if (unlikely(pmd_trans_huge(dst_pmdval))) {
+ err = -EEXIST;
+ break;
+ }
+ if (unlikely(pmd_none(dst_pmdval)) &&
+ unlikely(__pte_alloc(dst_mm, dst_pmd, dst_addr))) {
+ err = -ENOMEM;
+ break;
+ }
+ /* If an huge pmd materialized from under us fail */
+ if (unlikely(pmd_trans_huge(*dst_pmd))) {
+ err = -EFAULT;
+ break;
+ }
+
+ BUG_ON(pmd_none(*dst_pmd));
+ BUG_ON(pmd_trans_huge(*dst_pmd));
+
+ err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
+ src_addr, &page, zeropage);
+ cond_resched();
+
+ if (unlikely(err == -ENOENT)) {
+ void *page_kaddr;
+
+ up_read(&dst_mm->mmap_sem);
+ BUG_ON(!page);
+
+ page_kaddr = kmap(page);
+ err = copy_from_user(page_kaddr,
+ (const void __user *) src_addr,
+ PAGE_SIZE);
+ kunmap(page);
+ if (unlikely(err)) {
+ err = -EFAULT;
+ goto out;
+ }
+ goto retry;
+ } else
+ BUG_ON(page);
+
+ if (!err) {
+ dst_addr += PAGE_SIZE;
+ src_addr += PAGE_SIZE;
+ copied += PAGE_SIZE;
+
+ if (fatal_signal_pending(current))
+ err = -EINTR;
+ }
+ if (err)
+ break;
+ }
+
+out_unlock:
+ up_read(&dst_mm->mmap_sem);
+out:
+ if (page)
+ put_page(page);
+ BUG_ON(copied < 0);
+ BUG_ON(err > 0);
+ BUG_ON(!copied && !err);
+ return copied ? copied : err;
+}
+
+ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
+ unsigned long src_start, unsigned long len,
+ bool *mmap_changing)
+{
+ return __mcopy_atomic(dst_mm, dst_start, src_start, len, false,
+ mmap_changing);
+}
+
+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);
+}