linux-kernel - Re: [PATCH] rtc: ds1307: Fix relying on reset value for weekday

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 14 Jun 2016 16:39:48 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Keerthy <a0393675@...com>
Cc:	Keerthy <j-keerthy@...com>, a.zummo@...ertech.it, nm@...com,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: ds1307: Fix relying on reset value for weekday

On 07/06/2016 at 14:59:05 +0530, Keerthy wrote :
> Hi Alexandre,
> 
> On Wednesday 01 June 2016 06:06 PM, Keerthy wrote:
> > 
> > 
> > On Wednesday 01 June 2016 05:48 PM, Alexandre Belloni wrote:
> > > Hi,
> > > 
> > > On 01/06/2016 at 16:19:07 +0530, Keerthy wrote :
> > > > The reset value of weekday is 0x1. This is wrong since
> > > > the reset values of the day/month/year make up to Jan 1 2001.
> > > > When computed weekday comes out to be Monday. On a scale
> > > > of 1-7(Sunday - Saturday) it should be 0x2. So we should not
> > > > be relying on the reset value.
> > > > 
> > > 
> > > Hum, what are the chances that the reset value is actually the correct
> > > date/time?
> > > Won't that be corrected after the first call to set_time? Until then,
> > > the date is not correct so, do we care anyway?
> > 
> > Yes if an alarm is programmed without set_time.
> > 
> > ex: rtcwake -d /dev/rtc0 -s 5
> > 
> > Even the basic rtctest under tools/testing/selftests/timers/rtctest.c fails
> > as the wday is wrong and no alarm fires.
> > 
> > Instead of relying on some one to call set_time before programming alarm
> > its better to fix the wday to reflect the current day right?
> > 
> > 
> > > 
> > > Maybe I'm missing something here.
> 
> Let me know if you feel this is a valid fix.
> 

Well, this is probably a valid fix and I'll take it as is if I don't
find the time to make something more generic.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com