fscrypt: Don't use asynchronous CryptoAPI algorithms

Now that fscrypt's incomplete support for non-inline crypto engines has
been removed, and none of the CPU-based algorithms have the
CRYPTO_ALG_ASYNC flag set anymore, there is no need to accommodate
asynchronous algorithms.  Therefore, explicitly allocate only
synchronous algorithms.  Then, remove the code that handled waiting for
asynchronous en/decryption operations to complete.

This commit should *not* be backported to kernels that lack commit
0ba6ec5 ("crypto: x86/aes - stop using the SIMD helper"), as then
it would disable the use of the optimized AES code on x86.

Link: https://lore.kernel.org/r/20250710060754.637098-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

Author: Eric Biggers

fs/crypto/crypto.c

@@ -115,7 +115,6 @@ int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci,
 {
 	union fscrypt_iv iv;
 	struct skcipher_request *req = NULL;
-	DECLARE_CRYPTO_WAIT(wait);
 	struct scatterlist dst, src;
 	struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
 	int res = 0;
@@ -133,17 +132,17 @@ int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci,
 
 	skcipher_request_set_callback(
 		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
-		crypto_req_done, &wait);
+		NULL, NULL);
 
 	sg_init_table(&dst, 1);
 	sg_set_page(&dst, dest_page, len, offs);
 	sg_init_table(&src, 1);
 	sg_set_page(&src, src_page, len, offs);
 	skcipher_request_set_crypt(req, &src, &dst, len, &iv);
 	if (rw == FS_DECRYPT)
-		res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
+		res = crypto_skcipher_decrypt(req);
 	else
-		res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+		res = crypto_skcipher_encrypt(req);
 	skcipher_request_free(req);
 	if (res) {
 		fscrypt_err(ci->ci_inode,

fs/crypto/fname.c

@@ -95,7 +95,6 @@ int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
 			  u8 *out, unsigned int olen)
 {
 	struct skcipher_request *req = NULL;
-	DECLARE_CRYPTO_WAIT(wait);
 	const struct fscrypt_inode_info *ci = inode->i_crypt_info;
 	struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
 	union fscrypt_iv iv;
@@ -118,14 +117,14 @@ int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
 	req = skcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req)
 		return -ENOMEM;
-	skcipher_request_set_callback(req,
-			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
-			crypto_req_done, &wait);
+	skcipher_request_set_callback(
+		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+		NULL, NULL);
 	sg_init_one(&sg, out, olen);
 	skcipher_request_set_crypt(req, &sg, &sg, olen, &iv);
 
 	/* Do the encryption */
-	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+	res = crypto_skcipher_encrypt(req);
 	skcipher_request_free(req);
 	if (res < 0) {
 		fscrypt_err(inode, "Filename encryption failed: %d", res);
@@ -151,7 +150,6 @@ static int fname_decrypt(const struct inode *inode,
 			 struct fscrypt_str *oname)
 {
 	struct skcipher_request *req = NULL;
-	DECLARE_CRYPTO_WAIT(wait);
 	struct scatterlist src_sg, dst_sg;
 	const struct fscrypt_inode_info *ci = inode->i_crypt_info;
 	struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
@@ -162,9 +160,9 @@ static int fname_decrypt(const struct inode *inode,
 	req = skcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req)
 		return -ENOMEM;
-	skcipher_request_set_callback(req,
-		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
-		crypto_req_done, &wait);
+	skcipher_request_set_callback(
+		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+		NULL, NULL);
 
 	/* Initialize IV */
 	fscrypt_generate_iv(&iv, 0, ci);
@@ -173,7 +171,7 @@ static int fname_decrypt(const struct inode *inode,
 	sg_init_one(&src_sg, iname->name, iname->len);
 	sg_init_one(&dst_sg, oname->name, oname->len);
 	skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, &iv);
-	res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
+	res = crypto_skcipher_decrypt(req);
 	skcipher_request_free(req);
 	if (res < 0) {
 		fscrypt_err(inode, "Filename decryption failed: %d", res);

fs/crypto/fscrypt_private.h

@@ -59,8 +59,9 @@
  * Note that fscrypt also supports inline crypto engines.  Those don't use the
  * Crypto API and work much better than the old-style (non-inline) engines.
  */
-#define FSCRYPT_CRYPTOAPI_MASK \
-	(CRYPTO_ALG_ALLOCATES_MEMORY | CRYPTO_ALG_KERN_DRIVER_ONLY)
+#define FSCRYPT_CRYPTOAPI_MASK                            \
+	(CRYPTO_ALG_ASYNC | CRYPTO_ALG_ALLOCATES_MEMORY | \
+	 CRYPTO_ALG_KERN_DRIVER_ONLY)
 
 #define FSCRYPT_CONTEXT_V1	1
 #define FSCRYPT_CONTEXT_V2	2

fs/crypto/keysetup_v1.c

@@ -50,7 +50,6 @@ static int derive_key_aes(const u8 *master_key,
 {
 	int res = 0;
 	struct skcipher_request *req = NULL;
-	DECLARE_CRYPTO_WAIT(wait);
 	struct scatterlist src_sg, dst_sg;
 	struct crypto_skcipher *tfm =
 		crypto_alloc_skcipher("ecb(aes)", 0, FSCRYPT_CRYPTOAPI_MASK);
@@ -66,9 +65,9 @@ static int derive_key_aes(const u8 *master_key,
 		res = -ENOMEM;
 		goto out;
 	}
-	skcipher_request_set_callback(req,
-			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
-			crypto_req_done, &wait);
+	skcipher_request_set_callback(
+		req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+		NULL, NULL);
 	res = crypto_skcipher_setkey(tfm, nonce, FSCRYPT_FILE_NONCE_SIZE);
 	if (res < 0)
 		goto out;
@@ -77,7 +76,7 @@ static int derive_key_aes(const u8 *master_key,
 	sg_init_one(&dst_sg, derived_key, derived_keysize);
 	skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
 				   NULL);
-	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+	res = crypto_skcipher_encrypt(req);
 out:
 	skcipher_request_free(req);
 	crypto_free_skcipher(tfm);