smb/client: avoid dereferencing rdata=NULL in smb2_new_read_req()

JIRA: https://issues.redhat.com/browse/RHEL-57983

commit c724b2a
Author: Stefan Metzmacher <metze@samba.org>
Date:   Wed Aug 21 17:18:23 2024 +0200

    smb/client: avoid dereferencing rdata=NULL in smb2_new_read_req()
    
    This happens when called from SMB2_read() while using rdma
    and reaching the rdma_readwrite_threshold.
    
    Cc: stable@vger.kernel.org
    Fixes: a6559cc ("cifs: split out smb3_use_rdma_offload() helper")
    Reviewed-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Stefan Metzmacher <metze@samba.org>
    Signed-off-by: Steve French <stfrench@microsoft.com>

Signed-off-by: Paulo Alcantara <paalcant@redhat.com>

Author: pcacjr

fs/smb/client/smb2pdu.c

@@ -4437,7 +4437,7 @@ smb2_new_read_req(void **buf, unsigned int *total_len,
 	 * If we want to do a RDMA write, fill in and append
 	 * smbd_buffer_descriptor_v1 to the end of read request
 	 */
-	if (smb3_use_rdma_offload(io_parms)) {
+	if (rdata && smb3_use_rdma_offload(io_parms)) {
 		struct smbd_buffer_descriptor_v1 *v1;
 		bool need_invalidate = server->dialect == SMB30_PROT_ID;