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

From: Eric Biggers <[email-masked]>
Date: Sun, 29 Dec 2024 16:13:59 -0800

From: Eric Biggers <[email-masked]>

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 <[email-masked]>
Cc: Danny Tsen <[email-masked]>
Cc: Michael Ellerman <[email-masked]>
Cc: Naveen N Rao <[email-masked]>
Cc: Nicholas Piggin <[email-masked]>
Cc: [email-masked]
Signed-off-by: Eric Biggers <[email-masked]>
---

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);
 
 	if (enc)
 		ret = skcipher_walk_aead_encrypt(&walk, req, false);
 	else
-- 
2.47.1