4.14-stable review patch. If anyone has any objections, please let me know.
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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 Signed-off-by: Ben Hutchings ben.hutchings@codethink.co.uk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/extent-tree.c | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index fdc42eddccc2..83791d13c204 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -9828,6 +9828,8 @@ static int find_first_block_group(struct btrfs_fs_info *fs_info, 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); @@ -9862,8 +9864,32 @@ static int find_first_block_group(struct btrfs_fs_info *fs_info, "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(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(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;