Re: Git Bug Report: out of memory using git tag

> On Fri, Oct 28, 2022 at 03:29:33PM -0700, Martin Englund wrote:
> 
>> What did you do before the bug happened? (Steps to reproduce your issue)
>> I created a signed tag (git tag -s) using a ssh-agent key and then ran
>> git tag -l --format '%(contents:body)' v0.6.1
>>
>> What did you expect to happen? (Expected behavior)
>> I get the output
>>
>> What happened instead? (Actual behavior)
>> fatal: Out of memory, malloc failed (tried to allocate
>> 18446744073709551266 bytes)
> 
> Thanks for the report. This looks like pointer or size_t arithmetic that
> has gone negative. Here's a minimal reproduction:
> 
>   {
>     echo subject
>     echo "-----BEGIN PGP SIGNATURE-----"
>   } | git tag -F - foo
>   git tag -l --format='%(contents:body)' foo
> 
> The issue isn't unique to pgp signatures; the problem is in the parsing
> done by ref-filter's find_subpos(), so any signature type exhibits the
> problem. At the end of that function we do:
> 
>       *nonsiglen = sigstart - buf;
> 
> but "buf" has moved beyond "sigstart". Presumably because it uses
> strstr() to look for end-of-line in buf. Since there isn't one before
> the signature begins, we go to the end of the signature.
> 
> The bug bisects to 9f75ce3d8f (ref-filter: handle CRLF at end-of-line
> more gracefully, 2020-10-29). Before then, I think our loop was careful
> about moving past the start of the signature. Author cc'd.
>