diff --git a/include/sys/arc.h b/include/sys/arc.h
index 6328392bee23..215c75b6dfa3 100644
--- a/include/sys/arc.h
+++ b/include/sys/arc.h
@@ -125,15 +125,15 @@ typedef struct arc_buf_info {
 
 void arc_space_consume(uint64_t space, arc_space_type_t type);
 void arc_space_return(uint64_t space, arc_space_type_t type);
-arc_buf_t *arc_buf_alloc(spa_t *spa, int size, void *tag,
+arc_buf_t *arc_buf_alloc(spa_t *spa, uint64_t size, void *tag,
     arc_buf_contents_t type);
-arc_buf_t *arc_loan_buf(spa_t *spa, int size);
+arc_buf_t *arc_loan_buf(spa_t *spa, uint64_t size);
 void arc_return_buf(arc_buf_t *buf, void *tag);
 void arc_loan_inuse_buf(arc_buf_t *buf, void *tag);
 void arc_buf_add_ref(arc_buf_t *buf, void *tag);
 boolean_t arc_buf_remove_ref(arc_buf_t *buf, void *tag);
 void arc_buf_info(arc_buf_t *buf, arc_buf_info_t *abi, int state_index);
-int arc_buf_size(arc_buf_t *buf);
+uint64_t arc_buf_size(arc_buf_t *buf);
 void arc_release(arc_buf_t *buf, void *tag);
 int arc_released(arc_buf_t *buf);
 void arc_buf_sigsegv(int sig, siginfo_t *si, void *unused);
diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 2c7abe6ec542..b42bb4050032 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -1434,12 +1434,12 @@ arc_space_return(uint64_t space, arc_space_type_t type)
 }
 
 arc_buf_t *
-arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
+arc_buf_alloc(spa_t *spa, uint64_t size, void *tag, arc_buf_contents_t type)
 {
 	arc_buf_hdr_t *hdr;
 	arc_buf_t *buf;
 
-	ASSERT3U(size, >, 0);
+	VERIFY3U(size, <=, SPA_MAXBLOCKSIZE);
 	hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
 	ASSERT(BUF_EMPTY(hdr));
 	hdr->b_size = size;
@@ -1477,7 +1477,7 @@ static char *arc_onloan_tag = "onloan";
  * freed.
  */
 arc_buf_t *
-arc_loan_buf(spa_t *spa, int size)
+arc_loan_buf(spa_t *spa, uint64_t size)
 {
 	arc_buf_t *buf;
 
@@ -1837,7 +1837,7 @@ arc_buf_remove_ref(arc_buf_t *buf, void* tag)
 	return (no_callback);
 }
 
-int
+uint64_t
 arc_buf_size(arc_buf_t *buf)
 {
 	return (buf->b_hdr->b_size);
@@ -3307,6 +3307,22 @@ arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
 		enum zio_compress b_compress = ZIO_COMPRESS_OFF;
 		uint64_t b_asize = 0;
 
+		/*
+		 * Gracefully handle a damaged logical block size as a
+		 * checksum error by passing a dummy zio to the done callback.
+		 */
+		if (size > SPA_MAXBLOCKSIZE) {
+			if (done) {
+				rzio = zio_null(pio, spa, NULL,
+				    NULL, NULL, zio_flags);
+				rzio->io_error = ECKSUM;
+				done(rzio, buf, private);
+				zio_nowait(rzio);
+			}
+			rc = ECKSUM;
+			goto out;
+		}
+
 		if (hdr == NULL) {
 			/* this block is not in the cache */
 			arc_buf_hdr_t *exists = NULL;
diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index 76a8a99ab883..b31957094e08 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -571,12 +571,13 @@ dbuf_read_done(zio_t *zio, arc_buf_t *buf, void *vdb)
 	dbuf_rele_and_unlock(db, NULL);
 }
 
-static void
+static int
 dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 {
 	dnode_t *dn;
 	zbookmark_phys_t zb;
 	uint32_t aflags = ARC_NOWAIT;
+	int err;
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
@@ -601,7 +602,7 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 		dbuf_update_data(db);
 		db->db_state = DB_CACHED;
 		mutex_exit(&db->db_mtx);
-		return;
+		return (0);
 	}
 
 	/*
@@ -621,7 +622,7 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 		db->db_state = DB_CACHED;
 		*flags |= DB_RF_CACHED;
 		mutex_exit(&db->db_mtx);
-		return;
+		return (0);
 	}
 
 	DB_DNODE_EXIT(db);
@@ -640,12 +641,14 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 
 	dbuf_add_ref(db, NULL);
 
-	(void) arc_read(zio, db->db_objset->os_spa, db->db_blkptr,
+	err = arc_read(zio, db->db_objset->os_spa, db->db_blkptr,
 	    dbuf_read_done, db, ZIO_PRIORITY_SYNC_READ,
 	    (*flags & DB_RF_CANFAIL) ? ZIO_FLAG_CANFAIL : ZIO_FLAG_MUSTSUCCEED,
 	    &aflags, &zb);
 	if (aflags & ARC_CACHED)
 		*flags |= DB_RF_CACHED;
+
+	return (SET_ERROR(err));
 }
 
 int
@@ -688,11 +691,12 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
 
 		if (zio == NULL)
 			zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL);
-		dbuf_read_impl(db, zio, &flags);
+
+		err = dbuf_read_impl(db, zio, &flags);
 
 		/* dbuf_read_impl has dropped db_mtx for us */
 
-		if (prefetch)
+		if (!err && prefetch)
 			dmu_zfetch(&dn->dn_zfetch, db->db.db_offset,
 			    db->db.db_size, flags & DB_RF_CACHED);
 
@@ -700,7 +704,7 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
 			rw_exit(&dn->dn_struct_rwlock);
 		DB_DNODE_EXIT(db);
 
-		if (!havepzio)
+		if (!err && !havepzio)
 			err = zio_wait(zio);
 	} else {
 		/*