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Message-ID: <ab3b1aee-2140-2899-f37e-8f71ea67ea20@huaweicloud.com>
Date: Tue, 27 Dec 2022 11:51:52 +0100
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: dhowells@...hat.com, herbert@...dor.apana.org.au,
davem@...emloft.net, zohar@...ux.ibm.com,
dmitry.kasatkin@...il.com, paul@...l-moore.com, jmorris@...ei.org,
serge@...lyn.com, ebiggers@...nel.org
Cc: linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
Roberto Sassu <roberto.sassu@...wei.com>,
stable@...r.kernel.org
Subject: Re: [PATCH v4 2/2] KEYS: asymmetric: Copy sig and digest in
public_key_verify_signature()
On 12/27/2022 10:46 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.com>
>
> Commit ac4e97abce9b8 ("scatterlist: sg_set_buf() argument must be in linear
> mapping") checks that both the signature and the digest reside in the
> linear mapping area.
>
> However, more recently commit ba14a194a434c ("fork: Add generic vmalloced
> stack support"), made it possible to move the stack in the vmalloc area,
> which is not contiguous, and thus not suitable for sg_set_buf() which needs
> adjacent pages.
>
> Always make a copy of the signature and digest in the same buffer used to
> store the key and its parameters, and pass them to sg_set_buf(). Prefer it
> to conditionally doing the copy if necessary, to keep the code simple. The
> buffer allocated with kmalloc() is in the linear mapping area.
>
> Cc: stable@...r.kernel.org # 4.9.x
> Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> Link: https://lore.kernel.org/linux-integrity/Y4pIpxbjBdajymBJ@sol.localdomain/
> Suggested-by: Eric Biggers <ebiggers@...nel.org>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
> crypto/asymmetric_keys/public_key.c | 39 ++++++++++++++++-------------
> 1 file changed, 22 insertions(+), 17 deletions(-)
>
> diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
> index 2f8352e88860..a479e32cb280 100644
> --- a/crypto/asymmetric_keys/public_key.c
> +++ b/crypto/asymmetric_keys/public_key.c
> @@ -360,9 +360,10 @@ int public_key_verify_signature(const struct public_key *pkey,
> struct crypto_wait cwait;
> struct crypto_akcipher *tfm;
> struct akcipher_request *req;
> - struct scatterlist src_sg[2];
> + struct scatterlist src_sg;
> char alg_name[CRYPTO_MAX_ALG_NAME];
> - char *key, *ptr;
> + char *buf, *ptr;
> + size_t buf_len;
> int ret;
>
> pr_devel("==>%s()\n", __func__);
> @@ -400,34 +401,38 @@ int public_key_verify_signature(const struct public_key *pkey,
> if (!req)
> goto error_free_tfm;
>
> - key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
> - GFP_KERNEL);
> - if (!key)
> + buf_len = max_t(size_t, pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
> + sig->s_size + sig->digest_size);
> +
> + buf = kmalloc(buf_len, GFP_KERNEL);
> + if (!buf)
> goto error_free_req;
>
> - memcpy(key, pkey->key, pkey->keylen);
> - ptr = key + pkey->keylen;
> + memcpy(buf, pkey->key, pkey->keylen);
> + ptr = buf + pkey->keylen;
> ptr = pkey_pack_u32(ptr, pkey->algo);
> ptr = pkey_pack_u32(ptr, pkey->paramlen);
> memcpy(ptr, pkey->params, pkey->paramlen);
>
> if (pkey->key_is_private)
> - ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
> + ret = crypto_akcipher_set_priv_key(tfm, buf, pkey->keylen);
> else
> - ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
> + ret = crypto_akcipher_set_pub_key(tfm, buf, pkey->keylen);
> if (ret)
> - goto error_free_key;
> + goto error_free_buf;
>
> if (strcmp(pkey->pkey_algo, "sm2") == 0 && sig->data_size) {
> ret = cert_sig_digest_update(sig, tfm);
> if (ret)
> - goto error_free_key;
> + goto error_free_buf;
> }
>
> - sg_init_table(src_sg, 2);
> - sg_set_buf(&src_sg[0], sig->s, sig->s_size);
> - sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
> - akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
> + memcpy(buf, sig->s, sig->s_size);
> + memcpy(buf + sig->s_size, sig->digest, sig->digest_size);
> +
> + sg_init_table(&src_sg, 1);
> + sg_set_buf(&src_sg, buf, sig->s_size + sig->digest_size);
Ops, didn't commit the changes. Will send a new version soon.
Roberto
> + akcipher_request_set_crypt(req, &src_sg, NULL, sig->s_size,
> sig->digest_size);
> crypto_init_wait(&cwait);
> akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
> @@ -435,8 +440,8 @@ int public_key_verify_signature(const struct public_key *pkey,
> crypto_req_done, &cwait);
> ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
>
> -error_free_key:
> - kfree(key);
> +error_free_buf:
> + kfree(buf);
> error_free_req:
> akcipher_request_free(req);
> error_free_tfm:
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