linux-kernel - Re: [PATCH v2 10/29] crypto: powerpc/p10-aes-gcm - simplify handling of linear associated data

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Message-ID: <ec3515f1-f93a-4520-a9da-6ad14f9a6fe0@csgroup.eu>
Date: Thu, 2 Jan 2025 12:50:50 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Eric Biggers <ebiggers@...nel.org>, linux-crypto@...r.kernel.org
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Danny Tsen <dtsen@...ux.ibm.com>, Michael Ellerman <mpe@...erman.id.au>,
 Naveen N Rao <naveen@...nel.org>, Nicholas Piggin <npiggin@...il.com>,
 linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 10/29] crypto: powerpc/p10-aes-gcm - simplify handling
 of linear associated data



Le 30/12/2024 à 01:13, Eric Biggers a écrit :
> From: Eric Biggers <ebiggers@...gle.com>
> 
> p10_aes_gcm_crypt() is abusing the scatter_walk API to get the virtual
> address for the first source scatterlist element.  But this code is only
> built for PPC64 which is a !HIGHMEM platform, and it can read past a
> page boundary from the address returned by scatterwalk_map() which means
> it already assumes the address is from the kernel's direct map.  Thus,
> just use sg_virt() instead to get the same result in a simpler way.
> 
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Cc: Danny Tsen <dtsen@...ux.ibm.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Naveen N Rao <naveen@...nel.org>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> ---
> 
> This patch is part of a long series touching many files, so I have
> limited the Cc list on the full series.  If you want the full series and
> did not receive it, please retrieve it from lore.kernel.org.
> 
>   arch/powerpc/crypto/aes-gcm-p10-glue.c | 8 ++------
>   1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/crypto/aes-gcm-p10-glue.c b/arch/powerpc/crypto/aes-gcm-p10-glue.c
> index f37b3d13fc53..2862c3cf8e41 100644
> --- a/arch/powerpc/crypto/aes-gcm-p10-glue.c
> +++ b/arch/powerpc/crypto/aes-gcm-p10-glue.c
> @@ -212,11 +212,10 @@ static int p10_aes_gcm_crypt(struct aead_request *req, u8 *riv,
>   	struct p10_aes_gcm_ctx *ctx = crypto_tfm_ctx(tfm);
>   	u8 databuf[sizeof(struct gcm_ctx) + PPC_ALIGN];
>   	struct gcm_ctx *gctx = PTR_ALIGN((void *)databuf, PPC_ALIGN);
>   	u8 hashbuf[sizeof(struct Hash_ctx) + PPC_ALIGN];
>   	struct Hash_ctx *hash = PTR_ALIGN((void *)hashbuf, PPC_ALIGN);
> -	struct scatter_walk assoc_sg_walk;
>   	struct skcipher_walk walk;
>   	u8 *assocmem = NULL;
>   	u8 *assoc;
>   	unsigned int cryptlen = req->cryptlen;
>   	unsigned char ivbuf[AES_BLOCK_SIZE+PPC_ALIGN];
> @@ -232,12 +231,11 @@ static int p10_aes_gcm_crypt(struct aead_request *req, u8 *riv,
>   	memset(ivbuf, 0, sizeof(ivbuf));
>   	memcpy(iv, riv, GCM_IV_SIZE);
>   
>   	/* Linearize assoc, if not already linear */
>   	if (req->src->length >= assoclen && req->src->length) {
> -		scatterwalk_start(&assoc_sg_walk, req->src);
> -		assoc = scatterwalk_map(&assoc_sg_walk);
> +		assoc = sg_virt(req->src); /* ppc64 is !HIGHMEM */
>   	} else {
>   		gfp_t flags = (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) ?
>   			      GFP_KERNEL : GFP_ATOMIC;
>   
>   		/* assoc can be any length, so must be on heap */
> @@ -251,13 +249,11 @@ static int p10_aes_gcm_crypt(struct aead_request *req, u8 *riv,
>   
>   	vsx_begin();
>   	gcmp10_init(gctx, iv, (unsigned char *) &ctx->enc_key, hash, assoc, assoclen);
>   	vsx_end();
>   
> -	if (!assocmem)
> -		scatterwalk_unmap(assoc);
> -	else
> +	if (assocmem)
>   		kfree(assocmem);

kfree() accepts a NULL pointer, you can call kfree(assocmem) without 'if 
(assocmem)'


>   
>   	if (enc)
>   		ret = skcipher_walk_aead_encrypt(&walk, req, false);
>   	else