diff --git a/sys/powerpc/powerpc/busdma_machdep.c b/sys/powerpc/powerpc/busdma_machdep.c
--- a/sys/powerpc/powerpc/busdma_machdep.c
+++ b/sys/powerpc/powerpc/busdma_machdep.c
@@ -648,6 +648,7 @@
 		sgsize = MIN(buflen, PAGE_SIZE - (curaddr & PAGE_MASK));
 		if (map->pagesneeded != 0 && must_bounce(dmat, curaddr)) {
 			sgsize = roundup2(sgsize, dmat->alignment);
+			sgsize = MIN(sgsize, buflen);
 			curaddr = add_bounce_page(dmat, map, kvaddr, curaddr,
 			    sgsize);
 		}
diff --git a/sys/riscv/riscv/busdma_bounce.c b/sys/riscv/riscv/busdma_bounce.c
--- a/sys/riscv/riscv/busdma_bounce.c
+++ b/sys/riscv/riscv/busdma_bounce.c
@@ -672,6 +672,7 @@
 		    map->pagesneeded != 0 &&
 		    addr_needs_bounce(dmat, curaddr)) {
 			sgsize = roundup2(sgsize, dmat->common.alignment);
+			sgsize = MIN(sgsize, buflen);
 			curaddr = add_bounce_page(dmat, map, kvaddr, curaddr,
 			    sgsize);
 		} else if ((dmat->bounce_flags & BF_COHERENT) == 0) {
diff --git a/sys/x86/x86/busdma_bounce.c b/sys/x86/x86/busdma_bounce.c
--- a/sys/x86/x86/busdma_bounce.c
+++ b/sys/x86/x86/busdma_bounce.c
@@ -726,6 +726,7 @@
 		    map->pagesneeded != 0 &&
 		    must_bounce(dmat, curaddr)) {
 			sgsize = roundup2(sgsize, dmat->common.alignment);
+			sgsize = MIN(sgsize, buflen);
 			curaddr = add_bounce_page(dmat, map, kvaddr, curaddr, 0,
 			    sgsize);
 		}