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Date: Mon, 20 Jul 2026 08:21:17 +0200
From: Lukas Wunner <lukas@wunner.de>
To: Jiangshan Yi <yijiangshan@kylinos.cn>
Cc: dhowells@redhat.com, ignat@linux.win, herbert@gondor.apana.org.au,
	davem@davemloft.net, linux-kernel@vger.kernel.org,
	linux-crypto@vger.kernel.org, keyrings@vger.kernel.org,
	13667453960@163.com
Subject: Re: [PATCH] crypto: pkcs7 - Use constant-time message digest
 comparison
Message-ID: <al2-XdcuEYRbnFLw@wunner.de>
References: <20260720032316.210113-1-yijiangshan@kylinos.cn>
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In-Reply-To: <20260720032316.210113-1-yijiangshan@kylinos.cn>

On Mon, Jul 20, 2026 at 11:23:16AM +0800, Jiangshan Yi wrote:
> +++ b/crypto/asymmetric_keys/pkcs7_verify.c
> @@ -93,8 +94,8 @@ static int pkcs7_digest(struct pkcs7_message *pkcs7,
>  			goto error;
>  		}
>  
> -		if (memcmp(sig->m, sinfo->msgdigest,
> -			   sinfo->msgdigest_len) != 0) {
> +		if (crypto_memneq(sig->m, sinfo->msgdigest,
> +				  sinfo->msgdigest_len)) {
>  			pr_warn("Sig %u: Message digest doesn't match\n",
>  				sinfo->index);
>  			ret = -EKEYREJECTED;

The exact same patch was previously submitted by someone else
and rejected:

https://lore.kernel.org/all/alEsSl8i1_FpoU0f@fudgebox/T/#u