linux-kernel - Re: [PATCH] rtc: Initialized rtc_time->tm

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] [day] [month] [year] [list]

Message-ID: <CANcMJZBV5guSaP5kPKgfujoFJycNn9y8bYtZv6L7jpjnhkh6Hw@mail.gmail.com>
Date:	Fri, 12 Aug 2011 16:29:17 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Mike Waychison <mikew@...gle.com>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: Initialized rtc_time->tm_isdst

On Fri, Aug 12, 2011 at 2:04 PM, Mike Waychison <mikew@...gle.com> wrote:
> Even though the Linux kernel does not use the tm_isdst field, it is
> exposed as part of the ABI.  This field can accidentally be left
> initialized, which is why we currently memset buffers returned to
> userland in rtc_read_time.
>
> There is a case however where the field can return garbage from the
> stack though when using the RTC_ALM_READ ioctl on the rtc device.  This
> ioctl invokes rtc_read_alarm, which is careful to memset the rtc_wkalrm
> buffer that is copied to userland, but it then uses a struct copy to
> assign to alarm->time given the return value from rtc_ktime_to_tm().
>
> rtc_ktime_to_tm() is implemented by calling rtc_time_to_tm using a
> derivative seconds counds from ktime, but rtc_time_to_tm does not assign
> a value to ->tm_isdst.  This results in garbage from rtc_ktime_to_tm()'s
> frame ending up being copied out to userland as part of the returned
> rtc_wkalrm.

Thanks for catching this!  I've queued this in my tree.

thanks
-john
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/