KEYS: asymmetric: Copy sig and digest in public_key_verify_signature()

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>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>

diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
index eca5671ad3f2288eefe2a07b31d50b1a5728a8ed..50c933f86b218cca0ffe07756272dadbcf9854a2 100644 (file)
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -380,9 +380,10 @@ 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__);
@@ -420,34 +421,37 @@ 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 |
@@ -455,8 +459,8 @@ 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: