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

Christophe Leroy
2025-01-02T12:50:03Z

Le 30/12/2024 à 01:13, Eric Biggers a écrit :
> From: Eric Biggers <ebiggers@google.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@csgroup.eu>
> Cc: Danny Tsen <dtsen@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Naveen N Rao <naveen@kernel.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Eric Biggers <ebiggers@google.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