Merge tag '6.3-rc6-ksmbd-server-fix' of git://git.samba.org/ksmbd

Pull ksmbd server fix from Steve French:
 "smb311 server preauth integrity negotiate context parsing fix (check
  for out of bounds access)"

* tag '6.3-rc6-ksmbd-server-fix' of git://git.samba.org/ksmbd:
  ksmbd: avoid out of bounds access in decode_preauth_ctxt()

fs/ksmbd/smb2pdu.c

@@ -876,17 +876,21 @@ static void assemble_neg_contexts(struct ksmbd_conn *conn,
 }
 
 static __le32 decode_preauth_ctxt(struct ksmbd_conn *conn,
-				  struct smb2_preauth_neg_context *pneg_ctxt)
+				  struct smb2_preauth_neg_context *pneg_ctxt,
+				  int len_of_ctxts)
 {
-	__le32 err = STATUS_NO_PREAUTH_INTEGRITY_HASH_OVERLAP;
+	/*
+	 * sizeof(smb2_preauth_neg_context) assumes SMB311_SALT_SIZE Salt,
+	 * which may not be present. Only check for used HashAlgorithms[1].
+	 */
+	if (len_of_ctxts < MIN_PREAUTH_CTXT_DATA_LEN)
+		return STATUS_INVALID_PARAMETER;
 
-	if (pneg_ctxt->HashAlgorithms == SMB2_PREAUTH_INTEGRITY_SHA512) {
-		conn->preauth_info->Preauth_HashId =
-			SMB2_PREAUTH_INTEGRITY_SHA512;
-		err = STATUS_SUCCESS;
-	}
+	if (pneg_ctxt->HashAlgorithms != SMB2_PREAUTH_INTEGRITY_SHA512)
+		return STATUS_NO_PREAUTH_INTEGRITY_HASH_OVERLAP;
 
-	return err;
+	conn->preauth_info->Preauth_HashId = SMB2_PREAUTH_INTEGRITY_SHA512;
+	return STATUS_SUCCESS;
 }
 
 static void decode_encrypt_ctxt(struct ksmbd_conn *conn,
@@ -1014,7 +1018,8 @@ static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
 				break;
 
 			status = decode_preauth_ctxt(conn,
-						     (struct smb2_preauth_neg_context *)pctx);
+						     (struct smb2_preauth_neg_context *)pctx,
+						     len_of_ctxts);
 			if (status != STATUS_SUCCESS)
 				break;
 		} else if (pctx->ContextType == SMB2_ENCRYPTION_CAPABILITIES) {