[PATCH v3 21/21] s390/pkey/crypto: Introduce xflags param for pkey in-kernel API

Harald Freudenberger
2025-03-27T14:39:59Z

Add a new parameter xflags to the in-kernel API function
pkey_key2protkey(). Currently there is only one flag supported:

* PKEY_XFLAG_NOMEMALLOC:
If this flag is given in the xflags parameter, the pkey
implementation is not allowed to allocate memory but instead should
fall back to use preallocated memory or simple fail with -ENOMEM.
This flag is for protected key derive within a cipher or similar
which must not allocate memory which would cause io operations - see
also the CRYPTO_ALG_ALLOCATES_MEMORY flag in crypto.h.

The one and only user of this in-kernel API - the skcipher
implementations PAES in paes_s390.c set this flag upon request
to derive a protected key from the given raw key material.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
---
arch/s390/crypto/paes_s390.c | 2 +-
arch/s390/include/asm/pkey.h | 15 ++++++++++++++-
drivers/s390/crypto/pkey_api.c | 11 +++++++----
3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/arch/s390/crypto/paes_s390.c b/arch/s390/crypto/paes_s390.c
index 511093713a6f..646cbbf0678d 100644
--- a/arch/s390/crypto/paes_s390.c
+++ b/arch/s390/crypto/paes_s390.c
@@ -189,7 +189,7 @@ static inline int __paes_keyblob2pkey(const u8 *key, unsigned int keylen,
return -EINTR;
}
rc = pkey_key2protkey(key, keylen, pk->protkey, &pk->len,
- &pk->type);
+ &pk->type, PKEY_XFLAG_NOMEMALLOC);
}

return rc;
diff --git a/arch/s390/include/asm/pkey.h b/arch/s390/include/asm/pkey.h
index 5dca1a46a9f6..c0e7f8c25e9f 100644
--- a/arch/s390/include/asm/pkey.h
+++ b/arch/s390/include/asm/pkey.h
@@ -20,9 +20,22 @@
* @param key pointer to a buffer containing the key blob
* @param keylen size of the key blob in bytes
* @param protkey pointer to buffer receiving the protected key
+ * @param xflags additional execution flags (see PKEY_XFLAG_* definitions below)
+ * As of now the only supported flag is PKEY_XFLAG_NOMEMALLOC.
* @return 0 on success, negative errno value on failure
*/
int pkey_key2protkey(const u8 *key, u32 keylen,
- u8 *protkey, u32 *protkeylen, u32 *protkeytype);
+ u8 *protkey, u32 *protkeylen, u32 *protkeytype,
+ u32 xflags);
+
+/*
+ * If this flag is given in the xflags parameter, the pkey implementation
+ * is not allowed to allocate memory but instead should fall back to use
+ * preallocated memory or simple fail with -ENOMEM.
+ * This flag is for protected key derive within a cipher or similar
+ * which must not allocate memory which would cause io operations - see
+ * also the CRYPTO_ALG_ALLOCATES_MEMORY flag in crypto.h.
+ */
+#define PKEY_XFLAG_NOMEMALLOC 0x0001

#endif /* _KAPI_PKEY_H */
diff --git a/drivers/s390/crypto/pkey_api.c b/drivers/s390/crypto/pkey_api.c
index 55a4e70b866b..c46b57001550 100644
--- a/drivers/s390/crypto/pkey_api.c
+++ b/drivers/s390/crypto/pkey_api.c
@@ -53,17 +53,20 @@ static int key2protkey(const struct pkey_apqn *apqns, size_t nr_apqns,
* In-Kernel function: Transform a key blob (of any type) into a protected key
*/
int pkey_key2protkey(const u8 *key, u32 keylen,
- u8 *protkey, u32 *protkeylen, u32 *protkeytype)
+ u8 *protkey, u32 *protkeylen, u32 *protkeytype, u32 xflags)
{
+ u32 flags;
int rc;
- const u32 xflags = 0;
+
+ /* as of now only the NOMEMALLOC flag is supported */
+ flags = xflags & PKEY_XFLAG_NOMEMALLOC ? ZCRYPT_XFLAG_NOMEMALLOC : 0;

rc = key2protkey(NULL, 0, key, keylen,
- protkey, protkeylen, protkeytype, xflags);
+ protkey, protkeylen, protkeytype, flags);
if (rc == -ENODEV) {
pkey_handler_request_modules();
rc = key2protkey(NULL, 0, key, keylen,
- protkey, protkeylen, protkeytype, xflags);
+ protkey, protkeylen, protkeytype, flags);
}

return rc;
--
2.43.0