diff --git a/disk/part_dos.c b/disk/part_dos.c
index 89263d38aa..d6da3c0ec5 100644
--- a/disk/part_dos.c
+++ b/disk/part_dos.c
@@ -24,6 +24,10 @@
 
 #define DOS_PART_DEFAULT_SECTOR 512
 
+/* should this be configurable? It looks like it's not very common at all
+ * to use large numbers of partitions */
+#define MAX_EXT_PARTS 256
+
 /* Convert char[4] in little endian format to the host format integer
  */
 static inline int le32_to_int(unsigned char *le32)
@@ -109,6 +113,11 @@ static void print_partition_extended(block_dev_desc_t *dev_desc,
 	dos_partition_t *pt;
 	int i;
 
+	/* set a maximum recursion level */
+	if (part_num > MAX_EXT_PARTS) {
+		printf("** Nested DOS partitions detected, stopping **\n");
+		return;
+	}
 	if (dev_desc->block_read(dev_desc->dev, ext_part_sector, 1, (ulong *) buffer) != 1) {
 		printf ("** Can't read partition table on %d:%d **\n",
 			dev_desc->dev, ext_part_sector);
@@ -173,6 +182,12 @@ static int get_partition_info_extended (block_dev_desc_t *dev_desc, int ext_part
 	int i;
 	int dos_type;
 
+	/* set a maximum recursion level */
+	if (part_num > MAX_EXT_PARTS) {
+		printf("** Nested DOS partitions detected, stopping **\n");
+		return -1;
+	}
+
 	if (dev_desc->block_read (dev_desc->dev, ext_part_sector, 1, (ulong *) buffer) != 1) {
 		printf ("** Can't read partition table on %d:%d **\n",
 			dev_desc->dev, ext_part_sector);
diff --git a/fs/ext4/ext4fs.c b/fs/ext4/ext4fs.c
index 258b93791b..c0d063252d 100644
--- a/fs/ext4/ext4fs.c
+++ b/fs/ext4/ext4fs.c
@@ -63,11 +63,15 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
 	lbaint_t delayed_next = 0;
 	char *delayed_buf = NULL;
 	short status;
+	char *start_buf = buf;
 
 	/* Adjust len so it we can't read past the end of the file. */
 	if (len > filesize)
 		len = filesize;
 
+	if (blocksize <= 0 || len <= 0)
+		return -1;
+
 	blockcnt = lldiv(((len + pos) + blocksize - 1), blocksize);
 
 	for (i = lldiv(pos, blocksize); i < blockcnt; i++) {
@@ -127,6 +131,8 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
 					(blockend >> log2blksz);
 			}
 		} else {
+			int n;
+			int n_left;
 			if (previous_block_number != -1) {
 				/* spill */
 				status = ext4fs_devread(delayed_start,
@@ -137,7 +143,11 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
 					return -1;
 				previous_block_number = -1;
 			}
-			memset(buf, 0, blocksize - skipfirst);
+			n = blocksize - skipfirst;
+			n_left = len - ( buf - start_buf );
+			if (n > n_left)
+				n = n_left;
+			memset(buf, 0, n);
 		}
 		buf += blocksize - skipfirst;
 	}