btrfs: add checks for sys_chunk_array sizes

Verify that possible minimum and maximum size is set, validity of
contents is checked in btrfs_read_sys_array.

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1117136..263d147 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3911,6 +3911,25 @@
 	}
 
 	/*
+	 * Obvious sys_chunk_array corruptions, it must hold at least one key
+	 * and one chunk
+	 */
+	if (btrfs_super_sys_array_size(sb) > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE) {
+		printk(KERN_ERR "BTRFS: system chunk array too big %u > %u\n",
+				btrfs_super_sys_array_size(sb),
+				BTRFS_SYSTEM_CHUNK_ARRAY_SIZE);
+		ret = -EINVAL;
+	}
+	if (btrfs_super_sys_array_size(sb) < sizeof(struct btrfs_disk_key)
+			+ sizeof(struct btrfs_chunk)) {
+		printk(KERN_ERR "BTRFS: system chunk array too small %u < %lu\n",
+				btrfs_super_sys_array_size(sb),
+				sizeof(struct btrfs_disk_key)
+				+ sizeof(struct btrfs_chunk));
+		ret = -EINVAL;
+	}
+
+	/*
 	 * The generation is a global counter, we'll trust it more than the others
 	 * but it's still possible that it's the one that's wrong.
 	 */