cifs: Allocate memory for all iovs in smb2_ioctl

An IOCTL uses up to 2 iovs. The 1st iov is the command itself, the 2nd iov is
optional data for that command. The 1st iov is always allocated on the heap
but the 2nd iov may point to a variable on the stack. This will trigger an
error when passing the 2nd iov for RDMA I/O.

Fix this by allocating a buffer for the 2nd iov.
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie sahlberg <lsahlber@redhat.com>

fs/cifs/smb2pdu.c

@@ -2538,11 +2538,25 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
 	struct kvec *iov = rqst->rq_iov;
 	unsigned int total_len;
 	int rc;
+	char *in_data_buf;
 
 	rc = smb2_plain_req_init(SMB2_IOCTL, tcon, (void **) &req, &total_len);
 	if (rc)
 		return rc;
 
+	if (indatalen) {
+		/*
+		 * indatalen is usually small at a couple of bytes max, so
+		 * just allocate through generic pool
+		 */
+		in_data_buf = kmalloc(indatalen, GFP_NOFS);
+		if (!in_data_buf) {
+			cifs_small_buf_release(req);
+			return -ENOMEM;
+		}
+		memcpy(in_data_buf, in_data, indatalen);
+	}
+
 	req->CtlCode = cpu_to_le32(opcode);
 	req->PersistentFileId = persistent_fid;
 	req->VolatileFileId = volatile_fid;
@@ -2563,7 +2577,7 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
 		       cpu_to_le32(offsetof(struct smb2_ioctl_req, Buffer));
 		rqst->rq_nvec = 2;
 		iov[0].iov_len = total_len - 1;
-		iov[1].iov_base = in_data;
+		iov[1].iov_base = in_data_buf;
 		iov[1].iov_len = indatalen;
 	} else {
 		rqst->rq_nvec = 1;
@@ -2605,8 +2619,11 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
 void
 SMB2_ioctl_free(struct smb_rqst *rqst)
 {
-	if (rqst && rqst->rq_iov)
+	if (rqst && rqst->rq_iov) {
 		cifs_small_buf_release(rqst->rq_iov[0].iov_base); /* request */
+		if (rqst->rq_iov[1].iov_len)
+			kfree(rqst->rq_iov[1].iov_base);
+	}
 }