On Wed, Feb 07, 2018 at 05:18:25PM +0800, Qu Wenruo wrote:
> Strangely, we have level check in btrfs_print_tree() while we don't have
> the same check in read_node_slot().
>
> That's to say, for the following corruption, btrfs_search_slot() or
> btrfs_next_leaf() can return invalid leaf:
>
> Parent eb:
> node XXXXXX level 1
> ^^^^^^^
> Child should be leaf (level 0)
> ...
> key (XXX XXX XXX) block YYYYYY
>
> Child eb:
> leaf YYYYYY level 1
> ^^^^^^^
> Something went wrong now
>
> And for the corrupted leaf returned, later caller can be screwed up
> easily.
>
> Although the root cause (powerloss, but still something wrong breaking
> metadata CoW of btrfs) is still unknown, at least enhance btrfs-progs to
> avoid SEGV.
>
> Reported-by: Ralph Gauges <ralphgau...@googlemail.com>
> Signed-off-by: Qu Wenruo <w...@suse.com>
> ---
> ctree.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/ctree.c b/ctree.c
> index 4fc33b14000a..ddb1e9cc6d37 100644
> --- a/ctree.c
> +++ b/ctree.c
> @@ -22,6 +22,7 @@
> #include "repair.h"
> #include "internal.h"
> #include "sizes.h"
> +#include "messages.h"
>
> static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
> *root, struct btrfs_path *path, int level);
> @@ -640,7 +641,9 @@ static int bin_search(struct extent_buffer *eb, struct
> btrfs_key *key,
> struct extent_buffer *read_node_slot(struct btrfs_fs_info *fs_info,
> struct extent_buffer *parent, int slot)
> {
> + struct extent_buffer *ret;
> int level = btrfs_header_level(parent);
> +
> if (slot < 0)
> return NULL;
> if (slot >= btrfs_header_nritems(parent))
> @@ -649,8 +652,16 @@ struct extent_buffer *read_node_slot(struct
> btrfs_fs_info *fs_info,
> if (level == 0)
> return NULL;
>
> - return read_tree_block(fs_info, btrfs_node_blockptr(parent, slot),
> + ret = read_tree_block(fs_info, btrfs_node_blockptr(parent, slot),
The result of read_tree_block should be checked before use, by
extent_buffer_uptodate, null check or IS_ERR at least (depending on the
context of use).
> btrfs_node_ptr_generation(parent, slot));
> + if (btrfs_header_level(ret) != level - 1) {
> + error("child eb corrupted: parent bytenr=%llu item=%d parent
> level=%d child level=%d",
> + btrfs_header_bytenr(parent), slot,
> + btrfs_header_level(parent), btrfs_header_level(ret));
> + free_extent_buffer(ret);
> + return ERR_PTR(-EIO);
> + }
> + return ret;
> }
>
> static int balance_level(struct btrfs_trans_handle *trans,
> --
> 2.16.1
>
> --
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