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 E188EC433EF for ; Mon, 20 Jun 2022 14:04:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244329AbiFTOEO (ORCPT ); Mon, 20 Jun 2022 10:04:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245588AbiFTOC2 (ORCPT ); Mon, 20 Jun 2022 10:02:28 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCB4D1AF25; Mon, 20 Jun 2022 06:26:57 -0700 (PDT) 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 91724B811E1; Mon, 20 Jun 2022 13:16:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E07F9C3411B; Mon, 20 Jun 2022 13:16:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655731003; bh=OpoznZMK1Ok1ZJg+f5Ff1jh+Gv+HjqOFJILFgEo6XZU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=abEahYSbBqCdwkUfUpaH1/KuJt+MypLZIH8PxF9a/i1nrVXMVKbWrEMGnC4BFStiP u+N8fpIpTYJglAuFsC7rQvbjJ4Z9G+zXwdipEL3xsoSGDf9fhbH9IYWrHh5kJh7D8G pxzLVDUyobDuv/JuDp0olzC7maahvyM4uGu/rxSs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , "Jason A. Donenfeld" Subject: [PATCH 5.4 124/240] random: check for signal_pending() outside of need_resched() check Date: Mon, 20 Jun 2022 14:50:25 +0200 Message-Id: <20220620124742.606072992@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220620124737.799371052@linuxfoundation.org> References: <20220620124737.799371052@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jann Horn commit 1448769c9cdb69ad65287f4f7ab58bc5f2f5d7ba upstream. 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, signaling 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 Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -549,13 +549,13 @@ static ssize_t get_random_bytes_user(voi } do { - if (large_request && need_resched()) { + if (large_request) { if (signal_pending(current)) { if (!ret) ret = -ERESTARTSYS; break; } - schedule(); + cond_resched(); } chacha20_block(chacha_state, output);