[PATCH v3 2/8] ima: define ima_max_digest_data struct without a flexible array variable

[Mimi Zohar <zohar@xxxxxxxxxxxxx>]

Replace (the ugly) wrapping of the "ima_digest_data" struct, containing
a flexible array variable, inside another local structure, by defining
"ima_max_digest_data" struct with the maximum digest size.

For example, use the "ima_max_digest_data" struct when calculating the
"boot_aggregate" value.

Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
---
 security/integrity/ima/ima.h              |  2 +-
 security/integrity/ima/ima_crypto.c       |  2 +-
 security/integrity/ima/ima_init.c         |  9 +++------
 security/integrity/ima/ima_template_lib.c |  3 ++-
 security/integrity/integrity.h            | 24 +++++++++++++++++++++++
 5 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index be965a8715e4..78395bed7fad 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -144,7 +144,7 @@ int ima_calc_buffer_hash(const void *buf, loff_t len,
 			 struct ima_digest_data *hash);
 int ima_calc_field_array_hash(struct ima_field_data *field_data,
 			      struct ima_template_entry *entry);
-int ima_calc_boot_aggregate(struct ima_digest_data *hash);
+int ima_calc_boot_aggregate(struct ima_max_digest_data *hash);
 void ima_add_violation(struct file *file, const unsigned char *filename,
 		       struct integrity_iint_cache *iint,
 		       const char *op, const char *cause);
diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index a7206cc1d7d1..0ff1bfcaf13f 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -840,7 +840,7 @@ static int ima_calc_boot_aggregate_tfm(char *digest, u16 alg_id,
 	return rc;
 }
 
-int ima_calc_boot_aggregate(struct ima_digest_data *hash)
+int ima_calc_boot_aggregate(struct ima_max_digest_data *hash)
 {
 	struct crypto_shash *tfm;
 	u16 crypto_id, alg_id;
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index b26fa67476b4..dfbef713e0b6 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -47,16 +47,13 @@ static int __init ima_add_boot_aggregate(void)
 	struct integrity_iint_cache tmp_iint, *iint = &tmp_iint;
 	struct ima_event_data event_data = { .iint = iint,
 					     .filename = boot_aggregate_name };
+	struct ima_max_digest_data hash;
 	int result = -ENOMEM;
 	int violation = 0;
-	struct {
-		struct ima_digest_data hdr;
-		char digest[TPM_MAX_DIGEST_SIZE];
-	} hash;
 
 	memset(iint, 0, sizeof(*iint));
 	memset(&hash, 0, sizeof(hash));
-	iint->ima_hash = &hash.hdr;
+	iint->ima_hash = (struct ima_digest_data *)&hash;
 	iint->ima_hash->algo = ima_hash_algo;
 	iint->ima_hash->length = hash_digest_size[ima_hash_algo];
 
@@ -73,7 +70,7 @@ static int __init ima_add_boot_aggregate(void)
 	 * is not found.
 	 */
 	if (ima_tpm_chip) {
-		result = ima_calc_boot_aggregate(&hash.hdr);
+		result = ima_calc_boot_aggregate(&hash);
 		if (result < 0) {
 			audit_cause = "hashing_error";
 			goto err_out;
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index 5a5d462ab36d..d3aa511027cd 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -330,7 +330,8 @@ int ima_eventdigest_init(struct ima_event_data *event_data,
 	if ((const char *)event_data->filename == boot_aggregate_name) {
 		if (ima_tpm_chip) {
 			hash.hdr.algo = HASH_ALGO_SHA1;
-			result = ima_calc_boot_aggregate(&hash.hdr);
+			result = ima_calc_boot_aggregate(
+				(struct ima_max_digest_data *)&hash.hdr);
 
 			/* algo can change depending on available PCR banks */
 			if (!result && hash.hdr.algo != HASH_ALGO_SHA1)
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index d045dccd415a..ee2e6b7c7575 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -15,6 +15,7 @@
 #include <linux/types.h>
 #include <linux/integrity.h>
 #include <crypto/sha1.h>
+#include <crypto/hash.h>
 #include <linux/key.h>
 #include <linux/audit.h>
 
@@ -110,6 +111,29 @@ struct ima_digest_data {
 	u8 digest[];
 } __packed;
 
+/*
+ * Instead of dynamically allocating memory for the ima_digest_data struct
+ * with space for the specific hash algo or wrapping the ima_digest_data
+ * struct inside another local structure, define ima_max_digest_data struct
+ * with the maximum digest size.
+ */
+struct ima_max_digest_data {
+	u8 algo;
+	u8 length;
+	union {
+		struct {
+			u8 unused;
+			u8 type;
+		} sha1;
+		struct {
+			u8 type;
+			u8 algo;
+		} ng;
+		u8 data[2];
+	} xattr;
+	u8 digest[HASH_MAX_DIGESTSIZE];
+} __packed;
+
 /*
  * signature format v2 - for using with asymmetric keys
  */
-- 
2.27.0