diff --git a/sys/bus/cam/scsi/scsi_da.c b/sys/bus/cam/scsi/scsi_da.c
--- a/sys/bus/cam/scsi/scsi_da.c
+++ b/sys/bus/cam/scsi/scsi_da.c
@@ -1346,6 +1346,15 @@
 					int c = min(count, 0xffff);
 					int off = ranges * 8;
 
+					if (ranges >= softc->trim_max_ranges) {
+						/*
+						 * The TRIM data buffer is full.
+						 * Stop filling to avoid
+						 * overflowing req->data[].
+						 */
+						break;
+					}
+
 					req->data[off + 0] = lba & 0xff;
 					req->data[off + 1] = (lba >> 8) & 0xff;
 					req->data[off + 2] = (lba >> 16) & 0xff;