From patchwork Sat Feb 5 16:01:18 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: 540411 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 9435DC433F5 for ; Sat, 5 Feb 2022 16:02:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380360AbiBEQCW (ORCPT ); Sat, 5 Feb 2022 11:02:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380388AbiBEQCS (ORCPT ); Sat, 5 Feb 2022 11:02:18 -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 5444FC043181; Sat, 5 Feb 2022 08:02:08 -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 E0F3C60E8E; Sat, 5 Feb 2022 16:02:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE867C340E8; Sat, 5 Feb 2022 16:02:06 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="ABNM2uYZ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1644076926; 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=nqOp8nhL1np38W3ZS4UebvyfIj3gdR9UDopi2fA1DUQ=; b=ABNM2uYZ/Ez9idw+zh/cdtv68i7vMtvkB+owsLw7d9wtqeYJcoFnofRz/ZS32Z+i0ax2iG J/a6/bRODy17HtYE5YUOPfFRrL9GHSqbvCMhn46N0B/TKSFsZ5QN40qnm/bhdRgR/Sn2+/ Ow5Z0uxY8qMYuPS3xBgBiOE/jHS+Qpg= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id d859bc0c (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Sat, 5 Feb 2022 16:02:05 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org Cc: "Jason A. Donenfeld" , Sultan Alsawaf , Dominik Brodowski Subject: [PATCH v3 5/5] random: make credit_entropy_bits() always safe Date: Sat, 5 Feb 2022 17:01:18 +0100 Message-Id: <20220205160118.252698-6-Jason@zx2c4.com> In-Reply-To: <20220205160118.252698-1-Jason@zx2c4.com> References: <20220205160118.252698-1-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. Reported-by: Sultan Alsawaf Reviewed-by: Dominik Brodowski 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 82ec3a0399fb..8ae2bf5ca606 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -447,18 +447,15 @@ 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 { orig = READ_ONCE(input_pool.entropy_count); entropy_count = min(POOL_BITS, orig + nbits); @@ -470,18 +467,6 @@ static void credit_entropy_bits(int nbits) crng_reseed(&primary_crng); } -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 @@ -1526,7 +1511,10 @@ 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; @@ -1539,7 +1527,8 @@ 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: /*