From patchwork Fri Feb 4 13:53:25 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 12735122 X-Patchwork-Delegate: herbert@gondor.apana.org.au 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 0628CC433F5 for ; Fri, 4 Feb 2022 13:54:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1359127AbiBDNyR (ORCPT ); Fri, 4 Feb 2022 08:54:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1359151AbiBDNyG (ORCPT ); Fri, 4 Feb 2022 08:54:06 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ABD0AC06173E; Fri, 4 Feb 2022 05:54:05 -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 1D29D61C7B; Fri, 4 Feb 2022 13:54:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 195B3C004E1; Fri, 4 Feb 2022 13:54:04 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="Ho41945Y" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1643982843; 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: in-reply-to:in-reply-to:references:references; bh=u/MZ0szVCJI5WG41iXnMXaDPepbBJDhAp6vkKsxIFLE=; b=Ho41945YOfu9aR7VScAYHRaF2YGdzeGDmaElj3B8pgmfAREvG0C2zPLgkCbgsJS4us+2DN yjX9mfpLoh7Gij8thDP38uxHyTTHgLk8VPqIhGVqjdlawipw0d0TeKE8EvwmA/ON+cxg2V x9KO+LeoUKzCxyjKMKQtCkSmB5nURdc= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 4991711c (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Fri, 4 Feb 2022 13:54:03 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org Cc: "Jason A. Donenfeld" , Dominik Brodowski , Sultan Alsawaf Subject: [PATCH v2 4/4] random: make credit_entropy_bits() always safe Date: Fri, 4 Feb 2022 14:53:25 +0100 Message-Id: <20220204135325.8327-5-Jason@zx2c4.com> In-Reply-To: <20220204135325.8327-1-Jason@zx2c4.com> References: <20220204135325.8327-1-Jason@zx2c4.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@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 b4798a3f7bf6..455615ac169a 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -453,18 +453,15 @@ 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); @@ -476,18 +473,6 @@ 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 @@ -1534,7 +1519,10 @@ 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; @@ -1547,7 +1535,8 @@ 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: /*