Re: [PATCH] Avoid infinite loop in malformed packfiles

["René Scharfe" <l.s.r@web.de>]

Am 23.08.20 um 22:41 schrieb Ori Bernstein:
> On Sun, 23 Aug 2020 08:26:14 +0200, René Scharfe <l.s.r@web.de> wrote:
>
>> Am 23.08.20 um 05:11 schrieb Ori Bernstein:
>>> In packfile.c:1680, there's an infinite loop that tries to get
>>> to the base of a packfile. With offset deltas, the offset needs
>>> to be greater than 0, so it's always walking backwards, and the
>>> search is guaranteed to terminate.
>>>
>>> With reference deltas, there's no check for a cycle in the
>>> references, so a cyclic reference will cause git to loop
>>> infinitely, growing the delta_stack infinitely, which will
>>> cause it to consume all available memory as as a full CPU
>>> core.
>>
>> "as as"?  Perhaps "and"?
>
> I think I meant 'As well as' -- will fix.
>
>>
>> b5c0cbd8083 (pack-objects: use bitfield for object_entry::depth,
>> 2018-04-14) limited the delta depth for new packs to 4095, so 10000
>> seems reasonable.  Users with unreasonable packs would need to repack
>> them with an older version of Git, though.  Not sure if that would
>> affect anyone in practice.

> Is there anything you'd like me to do in this patch, other than fixing
> the typo?

Please explain in the commit message why 10000 is a good choice for that
new limit, and what users who happen to exceed it can do to regain
access to their packed data.

René