Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 619 insertions, 0 deletions

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
new file mode 100644
index 000000000..aae19c29b
--- /dev/null
+++ b/mm/userfaultfd.c
@@ -0,0 +1,619 @@
+/*
+ *  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;
+		}
+
+		flush_dcache_page(page);
+	} 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, mapping, idx);
+		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;
+			}
+			flush_dcache_page(page);
+			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);
+}