From patchwork Thu Sep 18 12:37:42 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Amos Kong X-Patchwork-Id: 4930741 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 76E7CBEEA5 for ; Thu, 18 Sep 2014 12:40:44 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 3BF2220166 for ; Thu, 18 Sep 2014 12:40:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 71F282015D for ; Thu, 18 Sep 2014 12:40:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755902AbaIRMkJ (ORCPT ); Thu, 18 Sep 2014 08:40:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41685 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751235AbaIRMiJ (ORCPT ); Thu, 18 Sep 2014 08:38:09 -0400 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s8ICbvhr016036 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 18 Sep 2014 08:37:57 -0400 Received: from air.redhat.com (vpn1-112-91.nay.redhat.com [10.66.112.91]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s8ICbmAL022426; Thu, 18 Sep 2014 08:37:53 -0400 From: Amos Kong To: virtualization@lists.linux-foundation.org Cc: kvm@vger.kernel.org, herbert@gondor.apana.org.au, m@bues.ch, mpm@selenic.com, amit.shah@redhat.com, rusty@rustcorp.com.au, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/6] hw_random: place mutex around read functions and buffers. Date: Thu, 18 Sep 2014 20:37:42 +0800 Message-Id: <1411043867-21109-2-git-send-email-akong@redhat.com> In-Reply-To: <1411043867-21109-1-git-send-email-akong@redhat.com> References: <1411043867-21109-1-git-send-email-akong@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Rusty Russell There's currently a big lock around everything, and it means that we can't query sysfs (eg /sys/devices/virtual/misc/hw_random/rng_current) while the rng is reading. This is a real problem when the rng is slow, or blocked (eg. virtio_rng with qemu's default /dev/random backend) This doesn't help (it leaves the current lock untouched), just adds a lock to protect the read function and the static buffers, in preparation for transition. Signed-off-by: Rusty Russell --- drivers/char/hw_random/core.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index aa30a25..b1b6042 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -53,7 +53,10 @@ static struct hwrng *current_rng; static struct task_struct *hwrng_fill; static LIST_HEAD(rng_list); +/* Protects rng_list and current_rng */ static DEFINE_MUTEX(rng_mutex); +/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */ +static DEFINE_MUTEX(reading_mutex); static int data_avail; static u8 *rng_buffer, *rng_fillbuf; static unsigned short current_quality; @@ -81,7 +84,9 @@ static void add_early_randomness(struct hwrng *rng) unsigned char bytes[16]; int bytes_read; + mutex_lock(&reading_mutex); bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1); + mutex_unlock(&reading_mutex); if (bytes_read > 0) add_device_randomness(bytes, bytes_read); } @@ -128,6 +133,7 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, int wait) { int present; + BUG_ON(!mutex_is_locked(&reading_mutex)); if (rng->read) return rng->read(rng, (void *)buffer, size, wait); @@ -160,13 +166,14 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, goto out_unlock; } + mutex_lock(&reading_mutex); if (!data_avail) { bytes_read = rng_get_data(current_rng, rng_buffer, rng_buffer_size(), !(filp->f_flags & O_NONBLOCK)); if (bytes_read < 0) { err = bytes_read; - goto out_unlock; + goto out_unlock_reading; } data_avail = bytes_read; } @@ -174,7 +181,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, if (!data_avail) { if (filp->f_flags & O_NONBLOCK) { err = -EAGAIN; - goto out_unlock; + goto out_unlock_reading; } } else { len = data_avail; @@ -186,7 +193,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, if (copy_to_user(buf + ret, rng_buffer + data_avail, len)) { err = -EFAULT; - goto out_unlock; + goto out_unlock_reading; } size -= len; @@ -194,6 +201,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf, } mutex_unlock(&rng_mutex); + mutex_unlock(&reading_mutex); if (need_resched()) schedule_timeout_interruptible(1); @@ -208,6 +216,9 @@ out: out_unlock: mutex_unlock(&rng_mutex); goto out; +out_unlock_reading: + mutex_unlock(&reading_mutex); + goto out_unlock; } @@ -348,13 +359,16 @@ static int hwrng_fillfn(void *unused) while (!kthread_should_stop()) { if (!current_rng) break; + mutex_lock(&reading_mutex); rc = rng_get_data(current_rng, rng_fillbuf, rng_buffer_size(), 1); + mutex_unlock(&reading_mutex); if (rc <= 0) { pr_warn("hwrng: no data available\n"); msleep_interruptible(10000); continue; } + /* Outside lock, sure, but y'know: randomness. */ add_hwgenerator_randomness((void *)rng_fillbuf, rc, rc * current_quality * 8 >> 10); }