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 00C88C433F5 for ; Fri, 4 Feb 2022 00:53:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356303AbiBDAxs (ORCPT ); Thu, 3 Feb 2022 19:53:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230386AbiBDAxq (ORCPT ); Thu, 3 Feb 2022 19:53:46 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4FBFDC061714 for ; Thu, 3 Feb 2022 16:53:46 -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 ams.source.kernel.org (Postfix) with ESMTPS id 9A3DAB83625 for ; Fri, 4 Feb 2022 00:53:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFD2CC340E8; Fri, 4 Feb 2022 00:53:42 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="T3/kD53Q" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1643936020; 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=uKFk+vFcUg3aqrCxmh17gVpNmWGCDQdqig8p98PcVKQ=; b=T3/kD53Q/cO+WsgDkaV3c+mjjX/g1wvbXRRC+3ICPtbX/JvRLjJVs3/vQ5ukfgeC16/e2F 030RULvYvXwYnl/MWbvT4trcPyWG4l1PQDLFCwdoaz6AbYIfb/DW0sGxtIgra1SgZtb/mS AD9ZAI2bsicP1dX6mbZ6ni4iAxPOO2g= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 1986c36f (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Fri, 4 Feb 2022 00:53:40 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org Cc: "Jason A. Donenfeld" , Dominik Brodowski , Sultan Alsawaf Subject: [PATCH] random: make credit_entropy_bits always safe Date: Fri, 4 Feb 2022 01:53:31 +0100 Message-Id: <20220204005331.67034-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is called from various hwgenerator drivers, so rather than having one "safe" version for userspace and one "unsafe" version for the kernel, just make everything safe; the checks are cheap and sensible to have anyway. Cc: Dominik Brodowski Reported-by: Sultan Alsawaf Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 29 +++++++++-------------------- 1 file changed, 9 insertions(+), 20 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index a1c681a616a6..7576a8b53c57 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -525,18 +525,15 @@ static void process_random_ready_list(void) spin_unlock_irqrestore(&random_ready_list_lock, flags); } -/* - * Credit (or debit) the entropy store with n bits of entropy. - * Use credit_entropy_bits_safe() if the value comes from userspace - * or otherwise should be checked for extreme values. - */ static void credit_entropy_bits(int nbits) { int entropy_count, orig; - if (!nbits) + if (nbits <= 0) return; + nbits = min(nbits, POOL_BITS); + do { entropy_count = orig = READ_ONCE(input_pool.entropy_count); entropy_count = min(POOL_BITS, entropy_count + nbits); @@ -548,18 +545,6 @@ static void credit_entropy_bits(int nbits) crng_reseed(&primary_crng, true); } -static int credit_entropy_bits_safe(int nbits) -{ - if (nbits < 0) - return -EINVAL; - - /* Cap the value to avoid overflows */ - nbits = min(nbits, POOL_BITS); - - credit_entropy_bits(nbits); - return 0; -} - /********************************************************************* * * CRNG using CHACHA20 @@ -1606,7 +1591,10 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) return -EPERM; if (get_user(ent_count, p)) return -EFAULT; - return credit_entropy_bits_safe(ent_count); + if (ent_count < 0) + return -EINVAL; + credit_entropy_bits(ent_count); + return 0; case RNDADDENTROPY: if (!capable(CAP_SYS_ADMIN)) return -EPERM; @@ -1619,7 +1607,8 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) retval = write_pool((const char __user *)p, size); if (retval < 0) return retval; - return credit_entropy_bits_safe(ent_count); + credit_entropy_bits(ent_count); + return 0; case RNDZAPENTCNT: case RNDCLEARPOOL: /* -- 2.35.0