Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4ce33762 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Greg Kroah-Hartman
Browse files

userfaultfd: shmem: add i_size checks 

commit e2a50c1f64145a04959df2442305d57307e5395a upstream.

With MAP_SHARED: recheck the i_size after taking the PT lock, to
serialize against truncate with the PT lock.  Delete the page from the
pagecache if the i_size_read check fails.

With MAP_PRIVATE: check the i_size after the PT lock before mapping
anonymous memory or zeropages into the MAP_PRIVATE shmem mapping.

A mostly irrelevant cleanup: like we do the delete_from_page_cache()
pagecache removal after dropping the PT lock, the PT lock is a spinlock
so drop it before the sleepable page lock.

Link: http://lkml.kernel.org/r/20181126173452.26955-5-aarcange@redhat.com


Fixes: 4c27fe4c ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support")
Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
Reviewed-by: default avatarMike Rapoport <rppt@linux.ibm.com>
Reviewed-by: default avatarHugh Dickins <hughd@google.com>
Reported-by: default avatarJann Horn <jannh@google.com>
Cc: <stable@vger.kernel.org>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6e44dd02

mm/shmem.c

+16 −2
Original line number Diff line number Diff line
@@ -2264,6 +2264,7 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 
	struct page *page;

	pte_t _dst_pte, *dst_pte;

	int ret;

	pgoff_t offset, max_off;



	ret = -ENOMEM;

	if (!shmem_inode_acct_block(inode, 1))
@@ -2301,6 +2302,12 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 
	__SetPageSwapBacked(page);

	__SetPageUptodate(page);



	ret = -EFAULT;

	offset = linear_page_index(dst_vma, dst_addr);

	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);

	if (unlikely(offset >= max_off))

		goto out_release;



	ret = mem_cgroup_try_charge_delay(page, dst_mm, gfp, &memcg, false);

	if (ret)

		goto out_release;
@@ -2319,8 +2326,14 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 
	if (dst_vma->vm_flags & VM_WRITE)

		_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));



	ret = -EEXIST;

	dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);



	ret = -EFAULT;

	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);

	if (unlikely(offset >= max_off))

		goto out_release_uncharge_unlock;



	ret = -EEXIST;

	if (!pte_none(*dst_pte))

		goto out_release_uncharge_unlock;
@@ -2338,13 +2351,14 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, 


	/* No need to invalidate - it was non-present before */

	update_mmu_cache(dst_vma, dst_addr, dst_pte);

	unlock_page(page);

	pte_unmap_unlock(dst_pte, ptl);

	unlock_page(page);

	ret = 0;

out:

	return ret;

out_release_uncharge_unlock:

	pte_unmap_unlock(dst_pte, ptl);

	delete_from_page_cache(page);

out_release_uncharge:

	mem_cgroup_cancel_charge(page, memcg, false);

out_release:

mm/userfaultfd.c

+24 −2
Original line number Diff line number Diff line
@@ -33,6 +33,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm, 
	void *page_kaddr;

	int ret;

	struct page *page;

	pgoff_t offset, max_off;

	struct inode *inode;



	if (!*pagep) {

		ret = -ENOMEM;
@@ -73,8 +75,17 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm, 
	if (dst_vma->vm_flags & VM_WRITE)

		_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));



	ret = -EEXIST;

	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;
@@ -108,11 +119,22 @@ static int mfill_zeropage_pte(struct mm_struct *dst_mm, 
	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));

	ret = -EEXIST;

	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);