2 files changed, 27 insertions, 0 deletions

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 71880299ed48..a69ed25af07f 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -76,6 +76,7 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
                 struct iov_iter *i, unsigned long offset, size_t bytes);
 void iov_iter_advance(struct iov_iter *i, size_t bytes);
 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
+int iov_iter_fault_in_multipages_readable(struct iov_iter *i, size_t bytes);
 size_t iov_iter_single_seg_count(const struct iov_iter *i);
 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
                          struct iov_iter *i);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 9d96e283520c..b80f84376b91 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -317,6 +317,32 @@ int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 }
 EXPORT_SYMBOL(iov_iter_fault_in_readable);
 
+/*
+ * Fault in one or more iovecs of the given iov_iter, to a maximum length of
+ * bytes.  For each iovec, fault in each page that constitutes the iovec.
+ *
+ * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
+ * because it is an invalid address).
+ */
+int iov_iter_fault_in_multipages_readable(struct iov_iter *i, size_t bytes)
+{
+        size_t skip = i->iov_offset;
+        const struct iovec *iov;
+        int err;
+        struct iovec v;
+
+        if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
+                iterate_iovec(i, bytes, v, iov, skip, ({
+                        err = fault_in_multipages_readable(v.iov_base,
+                                        v.iov_len);
+                        if (unlikely(err))
+                        return err;
+                0;}))
+        }
+        return 0;
+}
+EXPORT_SYMBOL(iov_iter_fault_in_multipages_readable);
+
 void iov_iter_init(struct iov_iter *i, int direction,
                         const struct iovec *iov, unsigned long nr_segs,
                         size_t count)