From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932119AbaIRCwG (ORCPT ); Wed, 17 Sep 2014 22:52:06 -0400 Received: from ozlabs.org ([103.22.144.67]:33545 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756264AbaIRCwB (ORCPT ); Wed, 17 Sep 2014 22:52:01 -0400 From: Rusty Russell To: Amos Kong , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, herbert@gondor.apana.org.au, m@bues.ch, mb@bu3sch.de, mpm@selenic.com, amit.shah@redhat.com, linux-kernel@vger.kernel.org Cc: Rusty Russell Subject: [PATCH 1/5] hw_random: place mutex around read functions and buffers. Date: Thu, 18 Sep 2014 12:18:22 +0930 Message-Id: <1411008506-28349-1-git-send-email-rusty@rustcorp.com.au> X-Mailer: git-send-email 1.9.1 In-Reply-To: <87wq91odhf.fsf@rustcorp.com.au> References: <87wq91odhf.fsf@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 aa30a25c8d49..b1b6042ad85c 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); } -- 1.9.1