btrfs: Check that each block group has corresponding chunk at mount time

commit 514c7dca85a0bf40be984dab0b477403a6db901f upstream.

A crafted btrfs image with incorrect chunk<->block group mapping will
trigger a lot of unexpected things as the mapping is essential.

Although the problem can be caught by block group item checker
added in "btrfs: tree-checker: Verify block_group_item", it's still not
sufficient.  A sufficiently valid block group item can pass the check
added by the mentioned patch but could fail to match the existing chunk.

This patch will add extra block group -> chunk mapping check, to ensure
we have a completely matching (start, len, flags) chunk for each block
group at mount time.

Here we reuse the original helper find_first_block_group(), which is
already doing the basic bg -> chunk checks, adding further checks of the
start/len and type flags.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=199837
Reported-by: Xu Wen <wen.xu@gatech.edu>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Su Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[bwh: Backported to 4.4: Use root->fs_info instead of fs_info]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1454938..f0f9538 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -9487,6 +9487,8 @@ static int find_first_block_group(struct btrfs_root *root,
        int ret = 0;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
+       struct btrfs_block_group_item bg;
+       u64 flags;
        int slot;
 
        ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
@@ -9521,8 +9523,32 @@ static int find_first_block_group(struct btrfs_root *root,
                        "logical %llu len %llu found bg but no related chunk",
                                          found_key.objectid, found_key.offset);
                                ret = -ENOENT;
+                       } else if (em->start != found_key.objectid ||
+                                  em->len != found_key.offset) {
+                               btrfs_err(root->fs_info,
+               "block group %llu len %llu mismatch with chunk %llu len %llu",
+                                         found_key.objectid, found_key.offset,
+                                         em->start, em->len);
+                               ret = -EUCLEAN;
                        } else {
-                               ret = 0;
+                               read_extent_buffer(leaf, &bg,
+                                       btrfs_item_ptr_offset(leaf, slot),
+                                       sizeof(bg));
+                               flags = btrfs_block_group_flags(&bg) &
+                                       BTRFS_BLOCK_GROUP_TYPE_MASK;
+
+                               if (flags != (em->map_lookup->type &
+                                             BTRFS_BLOCK_GROUP_TYPE_MASK)) {
+                                       btrfs_err(root->fs_info,
+"block group %llu len %llu type flags 0x%llx mismatch with chunk type flags 0x%llx",
+                                               found_key.objectid,
+                                               found_key.offset, flags,
+                                               (BTRFS_BLOCK_GROUP_TYPE_MASK &
+                                                em->map_lookup->type));
+                                       ret = -EUCLEAN;
+                               } else {
+                                       ret = 0;
+                               }
                        }
                        free_extent_map(em);
                        goto out;