Re: [PATCH v2] sparse index: fix use-after-free bug in cache_tree_verify()

> On 10/7/2021 5:50 AM, Phillip Wood via GitGitGadget wrote:
>> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>>
>> In a sparse index it is possible for the tree that is being verified
>> to be freed while it is being verified. This happens when the index is
>> sparse but the cache tree is not and index_name_pos() looks up a path
>> from the cache tree that is a descendant of a sparse index entry. That
>> triggers a call to ensure_full_index() which frees the cache tree that
>> is being verified.  Carrying on trying to verify the tree after this
>> results in a use-after-free bug. Instead restart the verification if a
>> sparse index is converted to a full index. This bug is triggered by a
>> call to reset_head() in "git rebase --apply". Thanks to René Scharfe
>> and Derick Stolee for their help analyzing the problem.
> 
> nit: s/Derick/Derrick/

> Otherwise, this version looks good to me. Thanks for putting the last
> bit of polish on it.
> 
> I'm taking this patch into our microsoft/git fork as we speak [1].
> 
> [1] https://github.com/microsoft/git/pull/439