Re: [PATCH 1/2] entry.c: convert checkout_entry to use strbuf

[Jeff King <peff@peff.net>]

On Wed, Oct 23, 2013 at 07:55:06PM +0700, Nguyen Thai Ngoc Duy wrote:

> The old code does not do boundary check so any paths longer than
> PATH_MAX can cause buffer overflow. Replace it with strbuf to handle
> paths of arbitrary length.

I think this is a reasonable solution. If we have such a long path, we
are probably about to feed it to open() or another syscall, and we will
just get ENAMETOOLONG there anyway. But certainly we need to fix the
buffer overflow, and we are probably better off letting the syscall
report failure than calling die(), because we generally handle the
syscall failure more gracefully (e.g., by reporting the failed path but
continuing).

> -	memcpy(path, state->base_dir, len);
> -	strcpy(path + len, ce->name);
> -	len += ce_namelen(ce);
> +	strbuf_reset(&path_buf);
> +	strbuf_addf(&path_buf, "%.*s%s", state->base_dir_len, state->base_dir, ce->name);
> +	path = path_buf.buf;
> +	len = path_buf.len;

This is not something you introduced, but while we are here, you may
want to use ce->namelen, which would be a little faster than treating it
as a string (especially for strbuf, as it can then know up front how big
the size is).

I doubt it's measurable, though (especially as the growth cost is
amortized due to the static buffer).

-Peff

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