Re: Segfault during fsck and spreading brokenness

From: Rich <forums@artfulrobot.uk>
Date: Sep 28, 2020, 06:43 UTC
Message-ID: <5cb3e4da-05ef-ac6a-2b8c-fab3137cdc68@artfulrobot.uk>
In-Reply-To: <20200925174718.GA70005@coredump.intra.peff.net>

Hi Jeff,

Thanks for a friendly and welcoming response (I was a bit scared posting here I suppose because the project's creator has a rep for not suffering fools!).

I copied the repo that causes a segfault on 2.11.0 to my laptop which runs 2.25.1 and I'm pleased to report that there's no segfault. I've posted the errors it does show below this message in case they're useful.

Show 5 quoted lines

>   What transport do you use between the two servers? The usual
> git-over-ssh and git-over-http protocols should be pretty resilient, but
> I would not be surprised if the old dumb-http protocol, which just
> downloads remote files wholesale, would be confused by a zero-length
> loose object file or similar.

The two servers are connected by SSH. As in:

% git config remote.origin.url sshalias:path/to/repo

where sshalias is defined in my .ssh/config file.

To test again,I made a bare clone of the fixed repo on my 2.25.1 host. I still had some dangling trees/blobs so I ran the following to make sure we were all clean:

git reflog expire --expire-unreachable=now --all git gc --prune=now git fsck --full

Then I added the broken repo as a remote (ssh) repo and ran fetch, which crashed (presumably correctly):

% git fetch broke error: object file ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833 is empty error: object file ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833 is empty fatal: loose object 3e9c7cd338d2ea3603d0c23b4b56902a04937833 (stored in ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833) is corrupt fatal: the remote end hung up unexpectedly

I re-ran fsck and it was still all clean. So 2.25.1 seems safe.I repeated the same procedure on the 2.11.0 version (Debian 10 host), and the same thing happened.

So I'm not sure what happened with the two repos getting broken at once; can't repeat it.

Let's hope that this was something that was fixed as you say!

Thanks, Rich

## Errors shown when running fsck on 2.25.1 on the broken repo:

git --version git version % git fsck --full error: object file ./objects/14/2d73242bba1e4aee89a887ec37d3b1ef00461c is empty error: unable to mmap ./objects/14/2d73242bba1e4aee89a887ec37d3b1ef00461c: No such file or directory error: 142d73242bba1e4aee89a887ec37d3b1ef00461c: object corrupt or missing: ./objects/14/2d73242bba1e4aee89a887ec37d3b1ef00461c error: object file ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833 is empty error: unable to mmap ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833: No such file or directory error: 3e9c7cd338d2ea3603d0c23b4b56902a04937833: object corrupt or missing: ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833 error: object file ./objects/45/aaa8e78abffa54ee2a620ef453d2b73443a3f9 is empty error: unable to mmap ./objects/45/aaa8e78abffa54ee2a620ef453d2b73443a3f9: No such file or directory error: 45aaa8e78abffa54ee2a620ef453d2b73443a3f9: object corrupt or missing: ./objects/45/aaa8e78abffa54ee2a620ef453d2b73443a3f9 error: object file ./objects/51/c79dda59372c0bd44457fbf810c66a6b184bb4 is empty error: unable to mmap ./objects/51/c79dda59372c0bd44457fbf810c66a6b184bb4: No such file or directory error: 51c79dda59372c0bd44457fbf810c66a6b184bb4: object corrupt or missing: ./objects/51/c79dda59372c0bd44457fbf810c66a6b184bb4 error: object file ./objects/92/92c90c7f01b5f9252a4631071d8ed39b121d52 is empty error: unable to mmap ./objects/92/92c90c7f01b5f9252a4631071d8ed39b121d52: No such file or directory error: 9292c90c7f01b5f9252a4631071d8ed39b121d52: object corrupt or missing: ./objects/92/92c90c7f01b5f9252a4631071d8ed39b121d52 error: object file ./objects/a0/1c6d43bb04b86b8263848c9d8daa20d4a68be4 is empty error: unable to mmap ./objects/a0/1c6d43bb04b86b8263848c9d8daa20d4a68be4: No such file or directory error: a01c6d43bb04b86b8263848c9d8daa20d4a68be4: object corrupt or missing: ./objects/a0/1c6d43bb04b86b8263848c9d8daa20d4a68be4 error: object file ./objects/c6/480c5f0be01c6860a17123bef79aa3fb98dd8b is empty error: unable to mmap ./objects/c6/480c5f0be01c6860a17123bef79aa3fb98dd8b: No such file or directory error: c6480c5f0be01c6860a17123bef79aa3fb98dd8b: object corrupt or missing: ./objects/c6/480c5f0be01c6860a17123bef79aa3fb98dd8b error: object file ./objects/e7/e8f34edee57ed77b240fa024df2f472dd9776d is empty error: unable to mmap ./objects/e7/e8f34edee57ed77b240fa024df2f472dd9776d: No such file or directory error: e7e8f34edee57ed77b240fa024df2f472dd9776d: object corrupt or missing: ./objects/e7/e8f34edee57ed77b240fa024df2f472dd9776d Checking object directories: 100% (256/256), done. Checking objects: 100% (310949/310949), done. error: object file ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833 is empty error: object file ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833 is empty fatal: loose object 3e9c7cd338d2ea3603d0c23b4b56902a04937833 (stored in ./objects/3e/9c7cd338d2ea3603d0c23b4b56902a04937833) is corrupt