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From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: Matheus Tavares Bernardino <matheus.bernardino@usp.br>
Cc: git <git@vger.kernel.org>,
	"Derrick Stolee" <dstolee@microsoft.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: [PATCH v2 01/13] hash: add an algo member to struct object_id
Date: Fri, 7 May 2021 20:07:51 +0000	[thread overview]
Message-ID: <YJWeF8iaWcegWACa@camp.crustytoothpaste.net> (raw)
In-Reply-To: <CAHd-oW4N7GB=E6hFc4GAD-b+1QzTR9+hL-hDXwAQkuss4Y4Ddw@mail.gmail.com>

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On 2021-05-07 at 13:58:42, Matheus Tavares Bernardino wrote:
> Hi, brian

Hey,

> 1. Make oidcpy() only copy `hash_algos[src->algo].rawsz` bytes. (But
> then we would probably need to branch in case `src->algo` is zero,
> right?)

Yeah, this will likely incur a performance cost.  I'd recommend avoiding
this if possible.

> 2. Reintroduce the oid_pad_buffer() function from your v1, and use it
> in parallel-checkout.c:send_one_item(), after oidcpy(). This would
> then zero out the copied uninitialized bytes (with the cost of one
> additional memcpy() per item, but this might be neglectable here).

This is fine with me.  I didn't have a use for it anymore, but you've
clearly found one, and I think this is probably the best approach here.

> 3. Use oidcpy() as-is, without additional padding, and let Valgrind
> warn. This false-positive warn might not be so problematic after all,
> and maybe I'm just overthinking things :)

I'm okay with this, but I don't know if the other end is security
sensitive and might need unused data zeroed.  If so, we should
definitely avoid this option.
-- 
brian m. carlson (he/him or they/them)
Houston, Texas, US

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  reply	other threads:[~2021-05-07 20:08 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-26  1:02 [PATCH v2 00/13] SHA-256 / SHA-1 interop, part 1 brian m. carlson
2021-04-26  1:02 ` [PATCH v2 01/13] hash: add an algo member to struct object_id brian m. carlson
2021-05-07 13:58   ` Matheus Tavares Bernardino
2021-05-07 20:07     ` brian m. carlson [this message]
2021-04-26  1:02 ` [PATCH v2 02/13] Always use oidread to read into " brian m. carlson
2021-04-26  1:02 ` [PATCH v2 03/13] http-push: set algorithm when reading object ID brian m. carlson
2021-04-26  1:02 ` [PATCH v2 04/13] hash: add a function to finalize object IDs brian m. carlson
2021-04-26  1:02 ` [PATCH v2 05/13] Use the final_oid_fn to finalize hashing of " brian m. carlson
2021-04-26  1:02 ` [PATCH v2 06/13] builtin/pack-redundant: avoid casting buffers to struct object_id brian m. carlson
2021-04-26  1:02 ` [PATCH v2 07/13] hash: set, copy, and use algo field in " brian m. carlson
2021-04-26  1:02 ` [PATCH v2 08/13] hash: provide per-algorithm null OIDs brian m. carlson
2021-04-26  1:02 ` [PATCH v2 09/13] builtin/show-index: set the algorithm for object IDs brian m. carlson
2021-04-26  1:02 ` [PATCH v2 10/13] commit-graph: don't store file hashes as struct object_id brian m. carlson
2021-04-26  1:02 ` [PATCH v2 11/13] builtin/pack-objects: avoid using struct object_id for pack hash brian m. carlson
2021-04-26  1:03 ` [PATCH v2 12/13] hex: default to the_hash_algo on zero algorithm value brian m. carlson
2021-04-26  1:03 ` [PATCH v2 13/13] hex: print objects using the hash algorithm member brian m. carlson

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