[PATCH v5 2/2] KEYS: asymmetric: Copy sig and digest in public_key_verify_signature()

Roberto Sassu
2022-12-27T14:29:25Z

From: Roberto Sassu <roberto.sassu@huawei.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_init_one(). 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@vger.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@kernel.org>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
crypto/asymmetric_keys/public_key.c | 38 ++++++++++++++++-------------
1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
index 2f8352e88860..49a3f7c01149 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 +401,37 @@ 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_one(&src_sg, buf, sig->s_size + sig->digest_size);
+ 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 +439,8 @@ 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:
--
2.25.1