From: PrasannaKumar Muralidharan Subject: Re: [PATCH] hw_random: core: Reset user selected rng by writing "" to rng_current Date: Mon, 30 Oct 2017 19:12:41 +0530 Message-ID: References: <20171027170404.21262-1-prasannatsmkumar@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Matt Mackall , Herbert Xu , "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" To: Harald Freudenberger Return-path: Received: from mail-io0-f193.google.com ([209.85.223.193]:44885 "EHLO mail-io0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932213AbdJ3Nmm (ORCPT ); Mon, 30 Oct 2017 09:42:42 -0400 Received: by mail-io0-f193.google.com with SMTP id m16so27217883iod.1 for ; Mon, 30 Oct 2017 06:42:42 -0700 (PDT) In-Reply-To: Sender: linux-crypto-owner@vger.kernel.org List-ID: Hi Harald, On 30 October 2017 at 18:58, Harald Freudenberger wrote: > On 10/27/2017 07:04 PM, PrasannaKumar Muralidharan wrote: >> 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; > Two lines later err is assigned the return value of mutex_lock_interruptible(). > So the -ENODEV value assignment does nothing. Indeed true. Will change this when I make a v2. I am even thinking if it makes sense to return error when user writes "" to rng_current and there is no rng device registered. I think returning 0 should be fine. >> 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); > looks like for me. > reviewed-by: Harald Freudenberger > Thank you. Thanks, PrasannaKumar