s390/pkey: Rework EP11 pkey handler to use stack for small memory allocs

There have been some places in the EP11 handler code where relatively
small amounts of memory have been allocated an freed at the end
of the function. This code has been reworked to use the stack instead.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Link: https://lore.kernel.org/r/20250424133619.16495-21-freude@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: hfreude

drivers/s390/crypto/pkey_ep11.c

@@ -186,7 +186,7 @@ static int ep11_key2protkey(const struct pkey_apqn *apqns, size_t nr_apqns,
 			    u8 *protkey, u32 *protkeylen, u32 *protkeytype)
 {
 	struct keytoken_header *hdr = (struct keytoken_header *)key;
-	struct pkey_apqn *local_apqns = NULL;
+	struct pkey_apqn _apqns[MAXAPQNSINLIST];
 	int i, rc;
 
 	if (keylen < sizeof(*hdr))
@@ -223,14 +223,10 @@ static int ep11_key2protkey(const struct pkey_apqn *apqns, size_t nr_apqns,
 	if (!apqns || (nr_apqns == 1 &&
 		       apqns[0].card == 0xFFFF && apqns[0].domain == 0xFFFF)) {
 		nr_apqns = MAXAPQNSINLIST;
-		local_apqns = kmalloc_array(nr_apqns, sizeof(struct pkey_apqn),
-					    GFP_KERNEL);
-		if (!local_apqns)
-			return -ENOMEM;
-		rc = ep11_apqns4key(key, keylen, 0, local_apqns, &nr_apqns);
+		rc = ep11_apqns4key(key, keylen, 0, _apqns, &nr_apqns);
 		if (rc)
 			goto out;
-		apqns = local_apqns;
+		apqns = _apqns;
 	}
 
 	for (rc = -ENODEV, i = 0; rc && i < nr_apqns; i++) {
@@ -259,7 +255,6 @@ static int ep11_key2protkey(const struct pkey_apqn *apqns, size_t nr_apqns,
 	}
 
 out:
-	kfree(local_apqns);
 	pr_debug("rc=%d\n", rc);
 	return rc;
 }
@@ -278,7 +273,7 @@ static int ep11_gen_key(const struct pkey_apqn *apqns, size_t nr_apqns,
 			u32 keybitsize, u32 flags,
 			u8 *keybuf, u32 *keybuflen, u32 *_keyinfo)
 {
-	struct pkey_apqn *local_apqns = NULL;
+	struct pkey_apqn _apqns[MAXAPQNSINLIST];
 	int i, len, rc;
 	const u32 xflags = 0;
 
@@ -315,15 +310,10 @@ static int ep11_gen_key(const struct pkey_apqn *apqns, size_t nr_apqns,
 	if (!apqns || (nr_apqns == 1 &&
 		       apqns[0].card == 0xFFFF && apqns[0].domain == 0xFFFF)) {
 		nr_apqns = MAXAPQNSINLIST;
-		local_apqns = kmalloc_array(nr_apqns, sizeof(struct pkey_apqn),
-					    GFP_KERNEL);
-		if (!local_apqns)
-			return -ENOMEM;
-		rc = ep11_apqns4type(subtype, NULL, NULL, 0,
-				     local_apqns, &nr_apqns);
+		rc = ep11_apqns4type(subtype, NULL, NULL, 0, _apqns, &nr_apqns);
 		if (rc)
 			goto out;
-		apqns = local_apqns;
+		apqns = _apqns;
 	}
 
 	for (rc = -ENODEV, i = 0; rc && i < nr_apqns; i++) {
@@ -333,7 +323,6 @@ static int ep11_gen_key(const struct pkey_apqn *apqns, size_t nr_apqns,
 	}
 
 out:
-	kfree(local_apqns);
 	pr_debug("rc=%d\n", rc);
 	return rc;
 }
@@ -353,7 +342,7 @@ static int ep11_clr2key(const struct pkey_apqn *apqns, size_t nr_apqns,
 			const u8 *clrkey, u32 clrkeylen,
 			u8 *keybuf, u32 *keybuflen, u32 *_keyinfo)
 {
-	struct pkey_apqn *local_apqns = NULL;
+	struct pkey_apqn _apqns[MAXAPQNSINLIST];
 	int i, len, rc;
 
 	/* check keytype, subtype, clrkeylen, keybitsize */
@@ -394,15 +383,10 @@ static int ep11_clr2key(const struct pkey_apqn *apqns, size_t nr_apqns,
 	if (!apqns || (nr_apqns == 1 &&
 		       apqns[0].card == 0xFFFF && apqns[0].domain == 0xFFFF)) {
 		nr_apqns = MAXAPQNSINLIST;
-		local_apqns = kmalloc_array(nr_apqns, sizeof(struct pkey_apqn),
-					    GFP_KERNEL);
-		if (!local_apqns)
-			return -ENOMEM;
-		rc = ep11_apqns4type(subtype, NULL, NULL, 0,
-				     local_apqns, &nr_apqns);
+		rc = ep11_apqns4type(subtype, NULL, NULL, 0, _apqns, &nr_apqns);
 		if (rc)
 			goto out;
-		apqns = local_apqns;
+		apqns = _apqns;
 	}
 
 	for (rc = -ENODEV, i = 0; rc && i < nr_apqns; i++) {
@@ -412,7 +396,6 @@ static int ep11_clr2key(const struct pkey_apqn *apqns, size_t nr_apqns,
 	}
 
 out:
-	kfree(local_apqns);
 	pr_debug("rc=%d\n", rc);
 	return rc;
 }
@@ -502,8 +485,8 @@ static int ep11_slowpath_key2protkey(const struct pkey_apqn *apqns,
 {
 	const struct keytoken_header *hdr = (const struct keytoken_header *)key;
 	const struct clearkeytoken *t = (const struct clearkeytoken *)key;
+	u8 tmpbuf[MAXEP11AESKEYBLOBSIZE]; /* 336 bytes */
 	u32 tmplen, keysize = 0;
-	u8 *tmpbuf;
 	int i, rc;
 
 	if (keylen < sizeof(*hdr))
@@ -515,11 +498,6 @@ static int ep11_slowpath_key2protkey(const struct pkey_apqn *apqns,
 	if (!keysize || t->len != keysize)
 		return -EINVAL;
 
-	/* alloc tmp key buffer */
-	tmpbuf = kmalloc(MAXEP11AESKEYBLOBSIZE, GFP_ATOMIC);
-	if (!tmpbuf)
-		return -ENOMEM;
-
 	/* try two times in case of failure */
 	for (i = 0, rc = -ENODEV; i < 2 && rc; i++) {
 		tmplen = MAXEP11AESKEYBLOBSIZE;
@@ -534,7 +512,6 @@ static int ep11_slowpath_key2protkey(const struct pkey_apqn *apqns,
 		pr_debug("ep11_key2protkey()=%d\n", rc);
 	}
 
-	kfree(tmpbuf);
 	pr_debug("rc=%d\n", rc);
 	return rc;
 }