Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_mirror.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_mirror.c	(revision 344128)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_mirror.c	(working copy)
@@ -219,9 +219,9 @@ vdev_mirror_map_init(zio_t *zio)
 		 * If we do not trust the pool config, some DVAs might be
 		 * invalid or point to vdevs that do not exist. We skip them.
 		 */
-		if (!spa_trust_config(spa)) {
-			ASSERT3U(zio->io_type, ==, ZIO_TYPE_READ);
+		if (zio->io_type == ZIO_TYPE_READ) {
 			int j = 0;
+
 			for (int i = 0; i < c; i++) {
 				if (zfs_dva_valid(spa, &dva[i], zio->io_bp))
 					dva_copy[j++] = dva[i];
@@ -228,7 +228,7 @@ vdev_mirror_map_init(zio_t *zio)
 			}
 			if (j == 0) {
 				zio->io_vsd = NULL;
-				zio->io_error = ENXIO;
+				zio->io_error = EIO;
 				return (NULL);
 			}
 			if (j < c) {
@@ -509,7 +509,6 @@ vdev_mirror_io_start(zio_t *zio)
 	mm = vdev_mirror_map_init(zio);
 
 	if (mm == NULL) {
-		ASSERT(!spa_trust_config(zio->io_spa));
 		ASSERT(zio->io_type == ZIO_TYPE_READ);
 		zio_execute(zio);
 		return;
Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zio.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zio.c	(revision 344128)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zio.c	(working copy)
@@ -839,6 +839,48 @@ zfs_blkptr_verify(spa_t *spa, const blkptr_t *bp)
 	}
 }
 
+static bool
+zfs_blkptr_valid(spa_t *spa, const blkptr_t *bp)
+{
+	if (!DMU_OT_IS_VALID(BP_GET_TYPE(bp))) {
+		printf("blkptr at %p has invalid TYPE %llu\n",
+		    bp, (longlong_t)BP_GET_TYPE(bp));
+		return (false);
+	}
+	if (BP_GET_CHECKSUM(bp) >= ZIO_CHECKSUM_FUNCTIONS ||
+	    BP_GET_CHECKSUM(bp) <= ZIO_CHECKSUM_ON) {
+		printf("blkptr at %p has invalid CHECKSUM %llu\n",
+		    bp, (longlong_t)BP_GET_CHECKSUM(bp));
+		return (false);
+	}
+	if (BP_GET_COMPRESS(bp) >= ZIO_COMPRESS_FUNCTIONS ||
+	    BP_GET_COMPRESS(bp) <= ZIO_COMPRESS_ON) {
+		printf("blkptr at %p has invalid COMPRESS %llu\n",
+		    bp, (longlong_t)BP_GET_COMPRESS(bp));
+		return (false);
+	}
+	if (BP_GET_LSIZE(bp) > SPA_MAXBLOCKSIZE) {
+		printf("blkptr at %p has invalid LSIZE %llu\n",
+		    bp, (longlong_t)BP_GET_LSIZE(bp));
+		return (false);
+	}
+	if (BP_GET_PSIZE(bp) > SPA_MAXBLOCKSIZE) {
+		printf("blkptr at %p has invalid PSIZE %llu\n",
+		    bp, (longlong_t)BP_GET_PSIZE(bp));
+		return (false);
+	}
+
+	if (BP_IS_EMBEDDED(bp)) {
+		if (BPE_GET_ETYPE(bp) > NUM_BP_EMBEDDED_TYPES) {
+			printf("blkptr at %p has invalid ETYPE %llu\n",
+			    bp, (longlong_t)BPE_GET_ETYPE(bp));
+			return (false);
+		}
+	}
+
+	return (true);
+}
+
 boolean_t
 zfs_dva_valid(spa_t *spa, const dva_t *dva, const blkptr_t *bp)
 {
@@ -876,8 +918,6 @@ zio_read(zio_t *pio, spa_t *spa, const blkptr_t *b
 {
 	zio_t *zio;
 
-	zfs_blkptr_verify(spa, bp);
-
 	zio = zio_create(pio, spa, BP_PHYSICAL_BIRTH(bp), bp,
 	    data, size, size, done, private,
 	    ZIO_TYPE_READ, priority, flags, NULL, 0, zb,
@@ -3182,6 +3222,13 @@ zio_vdev_io_start(zio_t *zio)
 		if (!(zio->io_flags & ZIO_FLAG_CONFIG_WRITER))
 			spa_config_enter(spa, SCL_ZIO, zio, RW_READER);
 
+		if (zio->io_type == ZIO_TYPE_READ &&
+		    !zfs_blkptr_valid(spa, zio->io_bp)) {
+			zio->io_error = EIO;
+			zio->io_vsd = NULL;
+			return (zio);
+		}
+
 		/*
 		 * The mirror_ops handle multiple DVAs in a single BP.
 		 */