Re: [PATCH] revision: fix missing null for freed memory

[Patrick Steinhardt <ps@pks.im>]

On Tue, Feb 11, 2025 at 04:29:09PM -0500, Jeff King wrote:
> On Tue, Feb 11, 2025 at 03:22:28PM -0500, D. Ben Knoble wrote:
> 
> > 2.{30,35}.0 fails to recognize --no-graph, so I checked "git log --grep no-graph
> > origin/master" with "git describe --contains" and decided that 2.36.0 was first
> > release recognizing --no-graph, but it didn't build for me (possibly an issue on
> > my end). I got 2.37.0 built, and it was "good," so that's where I started.
> > 
> > Here's my "bisect run" script.
> > 
> >     #! /bin/sh -x
> >     make || exit 125
> >     # segfault has exit >128
> >     ./bin-wrappers/git --no-pager log -2 --graph --no-graph --patch
> > --cc || exit 1
> 
> I don't think this is quite enough. The problem is a use-after-free, so
> the behavior is undefined. Depending on whether that heap block is
> reused, it might work just fine, or output garbage data, or segfault.
> 
> I'd have _thought_ it would usually just segfault, but it almost always
> just output garbage for me. Building with:
> 
>   make SANITIZE=address,undefined
> 
> is a good way to get reliable results for this kind of memory error.
> Doing that shows that v2.37.0 is actually bad. And bisecting shows that
> it has been broken since 087c745833 (log: add a --no-graph option,
> 2022-02-11), which is not too surprising.

Thanks all for bisecting :)

Patrick