On Tue, Jun 07, 2022 at 12:24:42AM -0400, Theodore Ts'o wrote:
> The kernel doesn't support extent trees deeper than 5
> (EXT4_MAX_EXTENT_DEPTH). For this reason we only maintain the extent
> tree statistics for 5 levels. Avoid out-of-bounds writes and reads if
> the extent tree is deeper than this.
>
> We keep these statistics to determine whether we should rebuild the
> extent tree. If the extent tree is too deep, we don't need the
> statistics because we should always rebuild the it.
Looks good.
Reviewed-by: Lukas Czerner <lczerner@xxxxxxxxxx>
>
> Reported-by: Nils Bars <nils.bars@xxxxxx>
> Reported-by: Moritz Schlögel <moritz.schloegel@xxxxxx>
> Reported-by: Nico Schiller <nico.schiller@xxxxxx>
> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
> ---
> e2fsck/extents.c | 10 +++++++++-
> e2fsck/pass1.c | 3 ++-
> 2 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/e2fsck/extents.c b/e2fsck/extents.c
> index 01879f56..86fe00e7 100644
> --- a/e2fsck/extents.c
> +++ b/e2fsck/extents.c
> @@ -526,7 +526,8 @@ errcode_t e2fsck_check_rebuild_extents(e2fsck_t ctx, ext2_ino_t ino,
> */
> if (info.curr_entry == 1 &&
> !(extent.e_flags & EXT2_EXTENT_FLAGS_SECOND_VISIT) &&
> - !eti.force_rebuild) {
> + !eti.force_rebuild &&
> + info.curr_level < MAX_EXTENT_DEPTH_COUNT) {
> struct extent_tree_level *etl;
>
> etl = eti.ext_info + info.curr_level;
> @@ -580,6 +581,13 @@ errcode_t e2fsck_should_rebuild_extents(e2fsck_t ctx,
> extents_per_block = (ctx->fs->blocksize -
> sizeof(struct ext3_extent_header)) /
> sizeof(struct ext3_extent);
> +
> + /* If the extent tree is too deep, then rebuild it. */
> + if (info->max_depth > MAX_EXTENT_DEPTH_COUNT) {
> + pctx->blk = info->max_depth;
> + op = PR_1E_CAN_COLLAPSE_EXTENT_TREE;
> + goto rebuild;
> + }
> /*
> * If we can consolidate a level or shorten the tree, schedule the
> * extent tree to be rebuilt.
> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> index 11d7ce93..43972e7c 100644
> --- a/e2fsck/pass1.c
> +++ b/e2fsck/pass1.c
> @@ -2842,7 +2842,8 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
> if (pctx->errcode)
> return;
> if (!(ctx->options & E2F_OPT_FIXES_ONLY) &&
> - !pb->eti.force_rebuild) {
> + !pb->eti.force_rebuild &&
> + info.curr_level < MAX_EXTENT_DEPTH_COUNT) {
> struct extent_tree_level *etl;
>
> etl = pb->eti.ext_info + info.curr_level;
> --
> 2.31.0
>
