X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=blobdiff_plain;f=fs%2Fuserfaultfd.c;h=7a85e609fc276f28dd80c8dc481e383094d1dfe9;hp=356d2b8568c1424d1d1935c451e65c7db13aab62;hb=5c848198aad3ad1c68309aa7002fa571a540568c;hpb=5b26f7180cdb3406404e6da78741e4e57f9a999e

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 356d2b8568c1..7a85e609fc27 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1361,6 +1361,19 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 		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 userfaultfd_ctx *ctx,
 		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
@@ -1560,6 +1574,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 		if (!vma->vm_userfaultfd_ctx.ctx)
 			goto skip;
 
+		WARN_ON(!(vma->vm_flags & VM_MAYWRITE));
+
 		if (vma->vm_start > start)
 			start = vma->vm_start;
 		vma_end = min(end, vma->vm_end);