ksmbd: fix incorrect validation for num_aces field of smb_acl

parse_dcal() validate num_aces to allocate posix_ace_state_array.

if (num_aces > ULONG_MAX / sizeof(struct smb_ace *))

It is an incorrect validation that we can create an array of size ULONG_MAX.
smb_acl has ->size field to calculate actual number of aces in request buffer
size. Use this to check invalid num_aces.

Reported-by: Igor Leite Ladessa <igor-ladessa@hotmail.com>
Tested-by: Igor Leite Ladessa <igor-ladessa@hotmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/smbacl.c

@@ -398,7 +398,9 @@ static void parse_dacl(struct mnt_idmap *idmap,
 	if (num_aces <= 0)
 		return;
 
-	if (num_aces > ULONG_MAX / sizeof(struct smb_ace *))
+	if (num_aces > (le16_to_cpu(pdacl->size) - sizeof(struct smb_acl)) /
+			(offsetof(struct smb_ace, sid) +
+			 offsetof(struct smb_sid, sub_auth) + sizeof(__le16)))
 		return;
 
 	ret = init_acl_state(&acl_state, num_aces);
@@ -432,6 +434,7 @@ static void parse_dacl(struct mnt_idmap *idmap,
 			offsetof(struct smb_sid, sub_auth);
 
 		if (end_of_acl - acl_base < acl_size ||
+		    ppace[i]->sid.num_subauth == 0 ||
 		    ppace[i]->sid.num_subauth > SID_MAX_SUB_AUTHORITIES ||
 		    (end_of_acl - acl_base <
 		     acl_size + sizeof(__le32) * ppace[i]->sid.num_subauth) ||