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 479CAC43334 for ; Thu, 23 Jun 2022 17:06:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230022AbiFWRGL (ORCPT ); Thu, 23 Jun 2022 13:06:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231519AbiFWREI (ORCPT ); Thu, 23 Jun 2022 13:04:08 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AFA2A517C5; Thu, 23 Jun 2022 09:55:27 -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 dfw.source.kernel.org (Postfix) with ESMTPS id CC16460B21; Thu, 23 Jun 2022 16:55:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A13DDC3411B; Thu, 23 Jun 2022 16:55:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1656003318; bh=1M9PSXJVnGE6mA3Iv9p2eOcKv5jmu9LVJ0s2Uepl+pg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hRKhQnqOHaTwNFui6JitdFi5A3FRkwfwMv69gm+fwuz8HxDn4esh/mSmWkS+utnxt 4RzKjYNhdOUCmfiWZ12Jtko/Mi/L0uP8x72wfUChyq4UKUzguNIlIoEBWhxF4yHJMX Zz9sMCfMJ1fxuZXASCTPR7MlpsE0zBQF5n9xFbLo= 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 4.9 172/264] random: check for signal_pending() outside of need_resched() check Date: Thu, 23 Jun 2022 18:42:45 +0200 Message-Id: <20220623164348.932310056@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220623164344.053938039@linuxfoundation.org> References: <20220623164344.053938039@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: linux-kernel@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 @@ -550,13 +550,13 @@ 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);