Re: pack corruption post-mortem

From: Duy Nguyen <pclouds@gmail.com>
Date: Oct 19, 2013, 10:32 UTC
Message-ID: <CACsJy8ABdE8mZMVFZkqYMC4ZeN_baWw=XcYOZYBCZytWP97rRw@mail.gmail.com>
In-Reply-To: <20131016083400.GA31266@sigill.intra.peff.net>

On Wed, Oct 16, 2013 at 3:34 PM, Jeff King <peff@peff.net> wrote:

Show 15 quoted lines

> I was recently presented with a repository with a corrupted packfile,
> and was asked if the data was recoverable. This post-mortem describes
> the steps I took to investigate and fix the problem. I thought others
> might find the process interesting, and it might help somebody in the
> same situation.
>
> I started with an fsck, which found a problem with exactly one object
> (I've used $pack and $obj below to keep the output readable, and also
> because I'll refer to them later):
>
>     $ git fsck
>     error: $pack SHA1 checksum mismatch
>     error: index CRC mismatch for object $obj from $pack at offset 51653873
>     error: inflate: data stream error (incorrect data check)
>     error: cannot unpack $obj from $pack at offset 51653873

I wonder if we should protect the sha-1 and pathname tables in packv4 with CRC too. A bit flipped in there could cause stream of corrupt objects and make it hard to pinpoint the corrupt location..

-- 
Duy