linux-kernel - [PATCH 3.16 022/245] btrfs: add more checks to btrfs_read_sys

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Message-ID: <lsq.1587683028.215054256@decadent.org.uk>
Date:   Fri, 24 Apr 2020 00:04:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "David Sterba" <dsterba@...e.cz>, "Chris Mason" <clm@...com>
Subject: [PATCH 3.16 022/245] btrfs: add more checks to btrfs_read_sys_array

3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: David Sterba <dsterba@...e.cz>

commit e3540eab29e1b2260bc4b9b3979a49a00e3e3af8 upstream.

Verify that the sys_array has enough bytes to read the next item.

Signed-off-by: David Sterba <dsterba@...e.cz>
Signed-off-by: Chris Mason <clm@...com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/btrfs/volumes.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6071,20 +6071,34 @@ int btrfs_read_sys_array(struct btrfs_ro
 
 	while (cur_offset < array_size) {
 		disk_key = (struct btrfs_disk_key *)array_ptr;
+		len = sizeof(*disk_key);
+		if (cur_offset + len > array_size)
+			goto out_short_read;
+
 		btrfs_disk_key_to_cpu(&key, disk_key);
 
-		len = sizeof(*disk_key);
 		array_ptr += len;
 		sb_array_offset += len;
 		cur_offset += len;
 
 		if (key.type == BTRFS_CHUNK_ITEM_KEY) {
 			chunk = (struct btrfs_chunk *)sb_array_offset;
+			/*
+			 * At least one btrfs_chunk with one stripe must be
+			 * present, exact stripe count check comes afterwards
+			 */
+			len = btrfs_chunk_item_size(1);
+			if (cur_offset + len > array_size)
+				goto out_short_read;
+
+			num_stripes = btrfs_chunk_num_stripes(sb, chunk);
+			len = btrfs_chunk_item_size(num_stripes);
+			if (cur_offset + len > array_size)
+				goto out_short_read;
+
 			ret = read_one_chunk(root, &key, sb, chunk);
 			if (ret)
 				break;
-			num_stripes = btrfs_chunk_num_stripes(sb, chunk);
-			len = btrfs_chunk_item_size(num_stripes);
 		} else {
 			ret = -EIO;
 			break;
@@ -6095,6 +6109,12 @@ int btrfs_read_sys_array(struct btrfs_ro
 	}
 	free_extent_buffer(sb);
 	return ret;
+
+out_short_read:
+	printk(KERN_ERR "BTRFS: sys_array too short to read %u bytes at offset %u\n",
+			len, cur_offset);
+	free_extent_buffer(sb);
+	return -EIO;
 }
 
 int btrfs_read_chunk_tree(struct btrfs_root *root)