Re: [PATCH v1 2/2] entry.c: check if file exists after checkout

[Jeff King <peff@peff.net>]

On Fri, Oct 06, 2017 at 01:26:48PM +0900, Junio C Hamano wrote:

> > We could probably be a bit more specific about the situation, since the
> > user will see this message with no context. Maybe something like:
> >
> >   unable to stat just-written file %s
> >
> > or something. We should probably also use error_errno(). I'd bet if this
> > ever triggers that it's likely to be ENOENT, but certainly if it _isn't_
> > that would be interesting information.
> 
> ENOTDIR and to a lesser degree EACCES and ELOOP are also
> uninteresting, as we are talking about somebody else mucking with
> the filesystem.

True. The nice thing about the error() route is that we don't need to
make such judgements. The user can decide what is unexpected.

> -- >8 --
> From: Lars Schneider <larsxschneider@gmail.com>
> Date: Thu, 5 Oct 2017 12:44:07 +0200
> Subject: [PATCH] entry.c: check if file exists after checkout
> 
> If we are checking out a file and somebody else racily deletes our file,
> then we would write garbage to the cache entry. Fix that by checking
> the result of the lstat() call on that file. Print an error to the user
> if the file does not exist.

I don't know if we wanted to capture any of the reasoning behind using
error() here or not. Frankly, I'm not sure how to argue for it
succinctly. :) I'm happy with letting it live on in the list archive.

> diff --git a/entry.c b/entry.c
> index f879758c73..6d9de3a5aa 100644
> --- a/entry.c
> +++ b/entry.c
> @@ -341,7 +341,9 @@ static int write_entry(struct cache_entry *ce,
>  	if (state->refresh_cache) {
>  		assert(state->istate);
>  		if (!fstat_done)
> -			lstat(ce->name, &st);
> +			if (lstat(ce->name, &st) < 0)
> +				return error_errno("unable stat just-written file %s",
> +						   ce->name);

s/unable stat/unable to stat/, I think.

Other than that, this looks fine to me.

-Peff