1 files changed, 10 insertions, 6 deletions

diff --git a/sys/kern/subr_mchain.c b/sys/kern/subr_mchain.c
index 4f0dab1bb6f2..dc70af2928c1 100644
--- a/sys/kern/subr_mchain.c
+++ b/sys/kern/subr_mchain.c
@@ -183,6 +183,7 @@ mb_put_mem(struct mbchain *mbp, c_caddr_t source, int size, int type)
 	caddr_t dst;
 	c_caddr_t src;
 	int cplen, error, mleft, count;
+	size_t srclen, dstlen;
 
 	m = mbp->mb_cur;
 	mleft = mbp->mb_mleft;
@@ -199,10 +200,13 @@ mb_put_mem(struct mbchain *mbp, c_caddr_t source, int size, int type)
 			continue;
 		}
 		cplen = mleft > size ? size : mleft;
+		srclen = dstlen = cplen;
 		dst = mtod(m, caddr_t) + m->m_len;
 		switch (type) {
 		    case MB_MCUSTOM:
-			error = mbp->mb_copy(mbp, source, dst, cplen);
+			srclen = size;
+			dstlen = mleft;
+			error = mbp->mb_copy(mbp, source, dst, &srclen, &dstlen);
 			if (error)
 				return error;
 			break;
@@ -222,11 +226,11 @@ mb_put_mem(struct mbchain *mbp, c_caddr_t source, int size, int type)
 			bzero(dst, cplen);
 			break;
 		}
-		size -= cplen;
-		source += cplen;
-		m->m_len += cplen;
-		mleft -= cplen;
-		mbp->mb_count += cplen;
+		size -= srclen;
+		source += srclen;
+		m->m_len += dstlen;
+		mleft -= dstlen;
+		mbp->mb_count += dstlen;
 	}
 	mbp->mb_cur = m;
 	mbp->mb_mleft = mleft;