+ userfaultfd-shmem-hugetlbfs-only-allow-to-register-vm_maywrite-vmas.patch added to -mm tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



The patch titled
     Subject: userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas
has been added to the -mm tree.  Its filename is
     userfaultfd-shmem-hugetlbfs-only-allow-to-register-vm_maywrite-vmas.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-shmem-hugetlbfs-only-allow-to-register-vm_maywrite-vmas.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-shmem-hugetlbfs-only-allow-to-register-vm_maywrite-vmas.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Subject: userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas

After the VMA to register the uffd onto is found, check that it has
VM_MAYWRITE set before allowing registration.  This way we inherit all
common code checks before allowing to fill file holes in shmem and
hugetlbfs with UFFDIO_COPY.

The userfaultfd memory model is not applicable for readonly files unless
it's a MAP_PRIVATE.

Link: http://lkml.kernel.org/r/20181126173452.26955-4-aarcange@xxxxxxxxxx
Fixes: ff62a3421044 ("hugetlb: implement memfd sealing")
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Reviewed-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support")
Cc: <stable@xxxxxxxxxxxxxxx>
Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---


--- a/fs/userfaultfd.c~userfaultfd-shmem-hugetlbfs-only-allow-to-register-vm_maywrite-vmas
+++ a/fs/userfaultfd.c
@@ -1361,6 +1361,19 @@ static int userfaultfd_register(struct u
 		ret = -EINVAL;
 		if (!vma_can_userfault(cur))
 			goto out_unlock;
+
+		/*
+		 * UFFDIO_COPY will fill file holes even without
+		 * PROT_WRITE. This check enforces that if this is a
+		 * MAP_SHARED, the process has write permission to the backing
+		 * file. If VM_MAYWRITE is set it also enforces that on a
+		 * MAP_SHARED vma: there is no F_WRITE_SEAL and no further
+		 * F_WRITE_SEAL can be taken until the vma is destroyed.
+		 */
+		ret = -EPERM;
+		if (unlikely(!(cur->vm_flags & VM_MAYWRITE)))
+			goto out_unlock;
+
 		/*
 		 * If this vma contains ending address, and huge pages
 		 * check alignment.
@@ -1406,6 +1419,7 @@ static int userfaultfd_register(struct u
 		BUG_ON(!vma_can_userfault(vma));
 		BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
 		       vma->vm_userfaultfd_ctx.ctx != ctx);
+		WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
 
 		/*
 		 * Nothing to do: this vma is already registered into this
@@ -1552,6 +1566,7 @@ static int userfaultfd_unregister(struct
 		cond_resched();
 
 		BUG_ON(!vma_can_userfault(vma));
+		WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
 
 		/*
 		 * Nothing to do: this vma is already registered into this
--- a/mm/userfaultfd.c~userfaultfd-shmem-hugetlbfs-only-allow-to-register-vm_maywrite-vmas
+++ a/mm/userfaultfd.c
@@ -205,8 +205,9 @@ retry:
 		if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
 			goto out_unlock;
 		/*
-		 * Only allow __mcopy_atomic_hugetlb on userfaultfd
-		 * registered ranges.
+		 * 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;
@@ -459,13 +460,9 @@ retry:
 	if (!dst_vma)
 		goto out_unlock;
 	/*
-	 * Be strict and only allow __mcopy_atomic on userfaultfd
-	 * registered ranges to prevent userland errors going
-	 * unnoticed. As far as the VM consistency is concerned, it
-	 * would be perfectly safe to remove this check, but there's
-	 * no useful usage for __mcopy_atomic ouside of userfaultfd
-	 * registered ranges. This is after all why these are ioctls
-	 * belonging to the userfaultfd and not syscalls.
+	 * 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;
_

Patches currently in -mm which might be from aarcange@xxxxxxxxxx are

userfaultfd-use-enoent-instead-of-efault-if-the-atomic-copy-user-fails.patch
userfaultfd-shmem-allocate-anonymous-memory-for-map_private-shmem.patch
userfaultfd-shmem-hugetlbfs-only-allow-to-register-vm_maywrite-vmas.patch
userfaultfd-shmem-add-i_size-checks.patch
userfaultfd-shmem-uffdio_copy-set-the-page-dirty-if-vm_write-is-not-set.patch




[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux