From: PrasannaKumar Muralidharan Subject: [PATCH] hw_random: core: Reset user selected rng by writing "" to rng_current Date: Fri, 27 Oct 2017 22:34:04 +0530 Message-ID: <20171027170404.21262-1-prasannatsmkumar@gmail.com> Cc: PrasannaKumar Muralidharan To: mpm@selenic.com, herbert@gondor.apana.org.au, freude@linux.vnet.ibm.com, linux-crypto@vger.kernel.org Return-path: Received: from mail-pf0-f193.google.com ([209.85.192.193]:54421 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751614AbdJ0RFK (ORCPT ); Fri, 27 Oct 2017 13:05:10 -0400 Received: by mail-pf0-f193.google.com with SMTP id n89so5358806pfk.11 for ; Fri, 27 Oct 2017 10:05:09 -0700 (PDT) Sender: linux-crypto-owner@vger.kernel.org List-ID: User is able to select a chosen rng by writing its name to rng_current but there is no way to reset it without unbinding the rng. Let user write "" to rng_current and delesect the chosen rng. Signed-off-by: PrasannaKumar Muralidharan --- drivers/char/hw_random/core.c | 51 +++++++++++++++++++++++++++---------------- 1 file changed, 32 insertions(+), 19 deletions(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 9701ac7..be03024 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -292,26 +292,48 @@ static struct miscdevice rng_miscdev = { .groups = rng_dev_groups, }; +static int enable_best_rng(void) +{ + int ret = -ENODEV; + + BUG_ON(!mutex_is_locked(&rng_mutex)); + + /* rng_list is sorted by quality, use the best (=first) one */ + if (!list_empty(&rng_list)) { + struct hwrng *new_rng; + + new_rng = list_entry(rng_list.next, struct hwrng, list); + ret = ((new_rng == current_rng) ? 0 : set_current_rng(new_rng)); + if (!ret) + cur_rng_set_by_user = 0; + } + + return ret; +} + static ssize_t hwrng_attr_current_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t len) { - int err; + int err = -ENODEV; struct hwrng *rng; err = mutex_lock_interruptible(&rng_mutex); if (err) return -ERESTARTSYS; - err = -ENODEV; - list_for_each_entry(rng, &rng_list, list) { - if (sysfs_streq(rng->name, buf)) { - err = 0; - cur_rng_set_by_user = 1; - if (rng != current_rng) + + if (sysfs_streq(buf, "")) { + err = enable_best_rng(); + } else { + list_for_each_entry(rng, &rng_list, list) { + if (sysfs_streq(rng->name, buf)) { + cur_rng_set_by_user = 1; err = set_current_rng(rng); - break; + break; + } } } + mutex_unlock(&rng_mutex); return err ? : len; @@ -493,17 +515,8 @@ void hwrng_unregister(struct hwrng *rng) mutex_lock(&rng_mutex); list_del(&rng->list); - if (current_rng == rng) { - drop_current_rng(); - cur_rng_set_by_user = 0; - /* rng_list is sorted by quality, use the best (=first) one */ - if (!list_empty(&rng_list)) { - struct hwrng *new_rng; - - new_rng = list_entry(rng_list.next, struct hwrng, list); - set_current_rng(new_rng); - } - } + if (current_rng == rng) + enable_best_rng(); if (list_empty(&rng_list)) { mutex_unlock(&rng_mutex); -- 2.10.0