[PATCH] keys: Use struct_size and size_add helper with alloc

[GUO Zihua <guozihua@huawei.com>]

Use struct_size helper for calculating size of flexible struct to avoid
potential issues and improve readibility. Use size_add to calculate
addition of size to prevent potential issues.

Reference: https://lore.kernel.org/all/CAHk-=wiGWjxs7EVUpccZEi6esvjpHJdgHQ=vtUeJ5crL62hx9A@mail.gmail.com/

Note: HASH_SIZE here is a SHA256_DIGEST_SIZE whoes value is 32, so
adding 1 should be fine here.

Signed-off-by: GUO Zihua <guozihua@huawei.com>
---
 security/keys/encrypted-keys/encrypted.c | 7 +++++--
 security/keys/user_defined.c             | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index e05cfc2e49ae..37349580e855 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -613,6 +613,7 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 	long dlen;
 	int i;
 	int ret;
+	size_t epayload_datalen = 0;
 
 	ret = kstrtol(datalen, 10, &dlen);
 	if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
@@ -667,8 +668,10 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 	if (ret < 0)
 		return ERR_PTR(ret);
 
-	epayload = kzalloc(sizeof(*epayload) + payload_datalen +
-			   datablob_len + HASH_SIZE + 1, GFP_KERNEL);
+	epayload_datalen = size_add(payload_datalen, datablob_len);
+	epayload_datalen = size_add(epayload_datalen, HASH_SIZE + 1);
+	epayload = kzalloc(struct_size(epayload, payload_data,
+				epayload_datalen), GFP_KERNEL);
 	if (!epayload)
 		return ERR_PTR(-ENOMEM);
 
diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c
index 749e2a4dcb13..334fed36e9f3 100644
--- a/security/keys/user_defined.c
+++ b/security/keys/user_defined.c
@@ -64,7 +64,7 @@ int user_preparse(struct key_preparsed_payload *prep)
 	if (datalen <= 0 || datalen > 32767 || !prep->data)
 		return -EINVAL;
 
-	upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
+	upayload = kmalloc(struct_size(upayload, data, datalen), GFP_KERNEL);
 	if (!upayload)
 		return -ENOMEM;
 
-- 
2.36.0