Btrfs: check items for correctness as we search

Currently if we have corrupted items things will blow up in spectacular ways.
So as we read in blocks and they are leaves, check the entire leaf to make sure
all of the items are correct and point to valid parts in the leaf for the item
data the are responsible for.  If the item is corrupt we will kick back EIO and
not read any of the copies since they are likely to not be correct either.  This
will catch generic corruptions, it will be up to the individual callers of
btrfs_search_slot to make sure their items are right.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 89 insertions, 1 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 495b1ac45f8c..9f31e110b481 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -323,6 +323,7 @@ static int btree_read_extent_buffer_pages(struct btrfs_root *root,
         int num_copies = 0;
         int mirror_num = 0;
 
+        clear_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
         io_tree = &BTRFS_I(root->fs_info->btree_inode)->io_tree;
         while (1) {
                 ret = read_extent_buffer_pages(io_tree, eb, start, 1,
@@ -331,6 +332,14 @@ static int btree_read_extent_buffer_pages(struct btrfs_root *root,
                     !verify_parent_transid(io_tree, eb, parent_transid))
                         return ret;
 
+                /*
+                 * This buffer's crc is fine, but its contents are corrupted, so
+                 * there is no reason to read the other copies, they won't be
+                 * any less wrong.
+                 */
+                if (test_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags))
+                        return ret;
+
                 num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
                                               eb->start, eb->len);
                 if (num_copies == 1)
@@ -419,6 +428,73 @@ static int check_tree_block_fsid(struct btrfs_root *root,
         return ret;
 }
 
+#define CORRUPT(reason, eb, root, slot)                         \
+        printk(KERN_CRIT "btrfs: corrupt leaf, %s: block=%llu," \
+               "root=%llu, slot=%d\n", reason,                  \
+               (unsigned long long)btrfs_header_bytenr(eb),     \
+               (unsigned long long)root->objectid, slot)
+
+static noinline int check_leaf(struct btrfs_root *root,
+                               struct extent_buffer *leaf)
+{
+        struct btrfs_key key;
+        struct btrfs_key leaf_key;
+        u32 nritems = btrfs_header_nritems(leaf);
+        int slot;
+
+        if (nritems == 0)
+                return 0;
+
+        /* Check the 0 item */
+        if (btrfs_item_offset_nr(leaf, 0) + btrfs_item_size_nr(leaf, 0) !=
+            BTRFS_LEAF_DATA_SIZE(root)) {
+                CORRUPT("invalid item offset size pair", leaf, root, 0);
+                return -EIO;
+        }
+
+        /*
+         * Check to make sure each items keys are in the correct order and their
+         * offsets make sense.  We only have to loop through nritems-1 because
+         * we check the current slot against the next slot, which verifies the
+         * next slot's offset+size makes sense and that the current's slot
+         * offset is correct.
+         */
+        for (slot = 0; slot < nritems - 1; slot++) {
+                btrfs_item_key_to_cpu(leaf, &leaf_key, slot);
+                btrfs_item_key_to_cpu(leaf, &key, slot + 1);
+
+                /* Make sure the keys are in the right order */
+                if (btrfs_comp_cpu_keys(&leaf_key, &key) >= 0) {
+                        CORRUPT("bad key order", leaf, root, slot);
+                        return -EIO;
+                }
+
+                /*
+                 * Make sure the offset and ends are right, remember that the
+                 * item data starts at the end of the leaf and grows towards the
+                 * front.
+                 */
+                if (btrfs_item_offset_nr(leaf, slot) !=
+                        btrfs_item_end_nr(leaf, slot + 1)) {
+                        CORRUPT("slot offset bad", leaf, root, slot);
+                        return -EIO;
+                }
+
+                /*
+                 * Check to make sure that we don't point outside of the leaf,
+                 * just incase all the items are consistent to eachother, but
+                 * all point outside of the leaf.
+                 */
+                if (btrfs_item_end_nr(leaf, slot) >
+                    BTRFS_LEAF_DATA_SIZE(root)) {
+                        CORRUPT("slot end outside of leaf", leaf, root, slot);
+                        return -EIO;
+                }
+        }
+
+        return 0;
+}
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 void btrfs_set_buffer_lockdep_class(struct extent_buffer *eb, int level)
 {
@@ -485,8 +561,20 @@ static int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
         btrfs_set_buffer_lockdep_class(eb, found_level);
 
         ret = csum_tree_block(root, eb, 1);
-        if (ret)
+        if (ret) {
                 ret = -EIO;
+                goto err;
+        }
+
+        /*
+         * If this is a leaf block and it is corrupt, set the corrupt bit so
+         * that we don't try and read the other copies of this block, just
+         * return -EIO.
+         */
+        if (found_level == 0 && check_leaf(root, eb)) {
+                set_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
+                ret = -EIO;
+        }
 
         end = min_t(u64, eb->len, PAGE_CACHE_SIZE);
         end = eb->start + end - 1;