Subject: Re: Bug encountered while comitting

From: Matthias Kestenholz <[email-masked]>
Date: Sat, 25 Mar 2006 02:15:27 +0100

* Junio C Hamano ([email-masked]) wrote:
> Matthias Kestenholz <[email-masked]> writes:
> 
> > The PHP script created directories under .git/objects which were
> > only writable by www-data. There were other directories which were
> > owned by user mk and group www-data, and they were group writable.
> >
> > So, I had write access to only a part of the .git directory.
> 
> core.sharedrepository perhaps?
> 
> While it probably is not a good idea to have you in www-data, it
> appears that is essentially you will end up doing, because PHP
> scripts that may _create_ new directories better not to have
> privilege to give newly created directories away to you (busting
> your quota), so they will be owned by www-data.www-data and for
> you to be able to write into it you either need to be www-data
> user or in www-data group, with core.sharedrepostiory set.
> 

Thanks for your answer; I did not know about this option (I should
probably re-read all the docs).

Anyway, I think git should never corrupt a repository, even if it
does not have the write permissions it needs.

The following commands were sufficient to create a corrupt
repository with git (v1.2.4-1, debian package):

$ git-init-db
$ echo test > file
$ git-update-index --add file ; git commit -m 'message'

repeat (f.e. 10 times):
$ echo test >> file
$ git-update-index file ; git commit -m 'message'

$ sudo chown root .git/objects/*

repeat the modification and commit commands until you get a message
similar to the following:

unable to write sha1 filename .git/objects/90/b33..: Permission denied
fatal: 90b33... is not a valid 'tree' object
unable to write sha1 filename .git/objects/ba/fe4..: Permission denied
error: file: failed to insert into database
fatal: Unable to process file file
etc...

The result of this all is: refs/heads/master might now point to a
non-existant commit object. Every git command now errors out with:

fatal: bad tree object HEAD

and git-log shows no output (probably since it does not find a
commit to begin with)

git-commit should abort as soon as it encounters an error and not
update HEAD.

Thanks,
Matthias

(Note: To find the last valid commit object, I could just scan the
objects directory for the recently modified files and write the sha1
value to refs/heads/master, so I had no data loss.)

-- 
:wq