diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c
index 061a305bf9c8..bba26a0355bb 100644
--- a/fs/smb/server/smbacl.c
+++ b/fs/smb/server/smbacl.c
@@ -1342,10 +1342,13 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,
 		ace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl));
 		aces_size = acl_size - sizeof(struct smb_acl);
 		for (i = 0; i < le16_to_cpu(pdacl->num_aces); i++) {
-			if (offsetof(struct smb_ace, access_req) > aces_size)
+			if (offsetof(struct smb_ace, sid) +
+			    aces_size < CIFS_SID_BASE_SIZE)
 				break;
 			ace_size = le16_to_cpu(ace->size);
-			if (ace_size > aces_size)
+			if (ace_size > aces_size ||
+			    ace_size < offsetof(struct smb_ace, sid) +
+				       CIFS_SID_BASE_SIZE)
 				break;
 			aces_size -= ace_size;
 			granted |= le32_to_cpu(ace->access_req);
@@ -1360,13 +1363,19 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,
 	ace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl));
 	aces_size = acl_size - sizeof(struct smb_acl);
 	for (i = 0; i < le16_to_cpu(pdacl->num_aces); i++) {
-		if (offsetof(struct smb_ace, access_req) > aces_size)
+		if (offsetof(struct smb_ace, sid) +
+		    aces_size < CIFS_SID_BASE_SIZE)
 			break;
 		ace_size = le16_to_cpu(ace->size);
-		if (ace_size > aces_size)
+		if (ace_size > aces_size ||
+		    ace_size < offsetof(struct smb_ace, sid) +
+			       CIFS_SID_BASE_SIZE)
 			break;
 		aces_size -= ace_size;
 
+		if (ace->sid.num_subauth > SID_MAX_SUB_AUTHORITIES)
+			break;
+
 		if (!compare_sids(&sid, &ace->sid) ||
 		    !compare_sids(&sid_unix_NFS_mode, &ace->sid)) {
 			found = 1;