1 files changed, 67 insertions, 0 deletions
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index a155e2de19aa..30a4226baf03 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1575,3 +1575,70 @@ unsigned int svc_fill_write_vector(struct svc_rqst *rqstp, struct kvec *first,
 	return i;
 }
 EXPORT_SYMBOL_GPL(svc_fill_write_vector);
+
+/**
+ * svc_fill_symlink_pathname - Construct pathname argument for VFS symlink call
+ * @rqstp: svc_rqst to operate on
+ * @first: buffer containing first section of pathname
+ * @total: total length of the pathname argument
+ *
+ * Returns pointer to a NUL-terminated string, or an ERR_PTR. The buffer is
+ * released automatically when @rqstp is recycled.
+ */
+char *svc_fill_symlink_pathname(struct svc_rqst *rqstp, struct kvec *first,
+				size_t total)
+{
+	struct xdr_buf *arg = &rqstp->rq_arg;
+	struct page **pages;
+	char *result;
+
+	/* VFS API demands a NUL-terminated pathname. This function
+	 * uses a page from @rqstp as the pathname buffer, to enable
+	 * direct placement. Thus the total buffer size is PAGE_SIZE.
+	 * Space in this buffer for NUL-termination requires that we
+	 * cap the size of the returned symlink pathname just a
+	 * little early.
+	 */
+	if (total > PAGE_SIZE - 1)
+		return ERR_PTR(-ENAMETOOLONG);
+
+	/* Some types of transport can present the pathname entirely
+	 * in rq_arg.pages. If not, then copy the pathname into one
+	 * page.
+	 */
+	pages = arg->pages;
+	WARN_ON_ONCE(arg->page_base != 0);
+	if (first->iov_base == 0) {
+		result = page_address(*pages);
+		result[total] = '\0';
+	} else {
+		size_t len, remaining;
+		char *dst;
+
+		result = page_address(*(rqstp->rq_next_page++));
+		dst = result;
+		remaining = total;
+
+		len = min_t(size_t, total, first->iov_len);
+		memcpy(dst, first->iov_base, len);
+		dst += len;
+		remaining -= len;
+
+		/* No more than one page left */
+		if (remaining) {
+			len = min_t(size_t, remaining, PAGE_SIZE);
+			memcpy(dst, page_address(*pages), len);
+			dst += len;
+		}
+
+		*dst = '\0';
+	}
+
+	/* Sanity check: we don't allow the pathname argument to
+	 * contain a NUL byte.
+	 */
+	if (strlen(result) != total)
+		return ERR_PTR(-EINVAL);
+	return result;
+}
+EXPORT_SYMBOL_GPL(svc_fill_symlink_pathname);