From nobody Fri Jun 19 08:32:03 2026 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 A8561C43217 for ; Wed, 6 Apr 2022 00:10:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1582641AbiDEXtC (ORCPT ); Tue, 5 Apr 2022 19:49:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1457759AbiDEQll (ORCPT ); Tue, 5 Apr 2022 12:41:41 -0400 Received: from mail-wr1-x432.google.com (mail-wr1-x432.google.com [IPv6:2a00:1450:4864:20::432]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D340BDB48B for ; Tue, 5 Apr 2022 09:39:42 -0700 (PDT) Received: by mail-wr1-x432.google.com with SMTP id h4so20148395wrc.13 for ; Tue, 05 Apr 2022 09:39:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=RaKfLsrc3XZWQqIO8eaNOg8ge8Ji7+/v6181V2TTNcc=; b=JraWzk1dVN/s3YPWE6AvnD8A2YawUca/c3wTpCGfOdGLOT8iR2qjz4I+fhRoLWBgX2 K7oMk4HbYHpaYL9fuNNWTai6d7Pj42JbBJlt2Gz+PD0fE9oqprY7L8ttYme+mU7z9Jy1 +lhTImI4F6qLi8PjuAJ/1obQWkx8AOn7vjMigrVpE/AN+8lDNchnUtVhW0Tck6xQmMfh iy0SNQ+ihW/IAfNCg1Nto4R8eELJSwOc9qtml31BHz5imNVjYjwvhOgHic2iVy40TQ5F CvQdLyDvYta1IFqW/lHpkZtgW694UNC7mEt+89LMaoBBneC9UnOYt1wfhoy+o1Zyo8zA w+3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=RaKfLsrc3XZWQqIO8eaNOg8ge8Ji7+/v6181V2TTNcc=; b=fJ8uIS+yY0L48c13Btu8fr8FH9spXtrwGARzPG43kicbFQTtpZ8i+cXOO+JsPQQPsp 7F/P09NlM9ei8fDVFbYql+m4HD+1EF4/b/aDReqqYyeo3Ud187yNvYTjE+zqdN1GIb7o 83/dtCUbV9Z15BVdKxEDnG1viYrUqNknrEA419w809LSRJHx2E7XzVZFEsjpDE/GyI/Y Kw6wi2K4V6pA84JqNKJLCnQtwA36IPulTNdYasYQ9QSI3tvkEXCbqqNavVEwORef8I+m sa9GtoOoU3L0giMU/zFiEjc9UQCd1GJHNy9X3hL13eA7ZbvKASQBJOAhbCL8AKJxdSaS RzdA== X-Gm-Message-State: AOAM531CwhVI4EQIFq0Ii4HzCwVjPjQpaTVEHW+1VY7PyS8cyqxcYWPm 2QZrhyuSqdr9dJfmwrrFjUmhUw== X-Google-Smtp-Source: ABdhPJzRwIFnGuM3S2npgVv4565/6c5hTUeCqw3z/u/h3ykqBZowMeUDAykTZGUr3Ql4am57RL0yCA== X-Received: by 2002:a05:6000:1a8d:b0:204:8cdb:279b with SMTP id f13-20020a0560001a8d00b002048cdb279bmr3365958wry.296.1649176781233; Tue, 05 Apr 2022 09:39:41 -0700 (PDT) Received: from localhost ([2a02:168:96c5:1:55ed:514f:6ad7:5bcc]) by smtp.gmail.com with ESMTPSA id k11-20020a5d6d4b000000b0020599079f68sm12454249wri.106.2022.04.05.09.39.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Apr 2022 09:39:40 -0700 (PDT) From: Jann Horn To: "Theodore Ts'o" , "Jason A . Donenfeld" Cc: linux-kernel@vger.kernel.org, Jann Horn Subject: [PATCH] random: Fix signal_pending() usage Date: Tue, 5 Apr 2022 18:39:31 +0200 Message-Id: <20220405163931.1108442-1-jannh@google.com> X-Mailer: git-send-email 2.35.1.1094.g7c7d902a7c-goog MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" signal_pending() checks TIF_NOTIFY_SIGNAL and TIF_SIGPENDING, which signal that the task should bail out of the syscall when possible. This is a separate concept from need_resched(), which checks TIF_NEED_RESCHED, signalling that the task should preempt. In particular, with the current code, the signal_pending() bailout probably won't work reliably. Change this to look like other functions that read lots of data, such as read_zero(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Jann Horn --- drivers/char/random.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 1eb220a5f44f..7f0253455d4e 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -540,13 +540,13 @@ static ssize_t get_random_bytes_user(void __user *buf= , size_t nbytes) crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE); =20 do { - if (large_request && need_resched()) { + if (large_request) { if (signal_pending(current)) { if (!ret) ret =3D -ERESTARTSYS; break; } - schedule(); + cond_resched(); } =20 chacha20_block(chacha_state, output); base-commit: 0c3e7b36d92681bba4c73c198a35e5a806d6f3ff --=20 2.35.1.1094.g7c7d902a7c-goog