From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F076C433F5 for ; Wed, 9 Feb 2022 17:45:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238400AbiBIRpS (ORCPT ); Wed, 9 Feb 2022 12:45:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232133AbiBIRpN (ORCPT ); Wed, 9 Feb 2022 12:45:13 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 76B48C0613C9 for ; Wed, 9 Feb 2022 09:45:15 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 11C6F61AFB for ; Wed, 9 Feb 2022 17:45:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E2472C340E7; Wed, 9 Feb 2022 17:45:13 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="F7r6o867" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1644428711; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=pRmKQrpG8Tp34SkPHizbt62a5hV7IZXO+3FlLtGN16M=; b=F7r6o867kDHVv7QPQow5ur+Cp3gWjCoHhRuq94k4Cp1eRXB/Uw9BvTwzuYH5xyS2ccEcKW V3bWhLmY1H0ty5D9zKus0+H7LUmkvTo51k36fAWgcnxozwXpqWFmsELPf+QqIMHqOveVoV 7BKP1e9991Jpr07l48BZCX/RA/rN3Ns= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 1cee3b28 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Wed, 9 Feb 2022 17:45:10 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org Cc: "Jason A. Donenfeld" , Dominik Brodowski , Jann Horn Subject: [PATCH] random: zero buffer after reading secret entropy from userspace Date: Wed, 9 Feb 2022 18:44:56 +0100 Message-Id: <20220209174456.644232-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This buffer may contain entropic data that shouldn't stick around longer than needed, zero it out our temporary buffer at the end of write_pool(). Cc: Dominik Brodowski Cc: Jann Horn Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 81cfbbf5f462..9c7a0297a7d4 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1357,19 +1357,24 @@ static __poll_t random_poll(struct file *file, poll_table *wait) static int write_pool(const char __user *ubuf, size_t count) { size_t len; + int ret = 0; u8 block[BLAKE2S_BLOCK_SIZE]; while (count) { len = min(count, sizeof(block)); - if (copy_from_user(block, ubuf, len)) - return -EFAULT; + if (copy_from_user(block, ubuf, len)) { + ret = -EFAULT; + goto out; + } count -= len; ubuf += len; mix_pool_bytes(block, len); cond_resched(); } - return 0; +out: + memzero_explicit(block, sizeof(block)); + return ret; } static ssize_t random_write(struct file *file, const char __user *buffer, -- 2.35.0