linux-kernel - [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-next>] [day] [month] [year] [list]

Message-Id: <1313183070-16724-1-git-send-email-mikew@google.com>
Date:	Fri, 12 Aug 2011 14:04:30 -0700
From:	Mike Waychison <mikew@...gle.com>
To:	Alessandro Zummo <a.zummo@...ertech.it>
Cc:	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org,
	Mike Waychison <mikew@...gle.com>
Subject: [PATCH] rtc: Initialized rtc_time->tm_isdst

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.

Fix this by initializing rtc_time->tm_isdst to 0 in rtc_time_to_tm.

Signed-off-by: Mike Waychison <mikew@...gle.com>
---
 drivers/rtc/rtc-lib.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c
index 075f170..c4cf057 100644
--- a/drivers/rtc/rtc-lib.c
+++ b/drivers/rtc/rtc-lib.c
@@ -85,6 +85,8 @@ void rtc_time_to_tm(unsigned long time, struct rtc_time *tm)
 	time -= tm->tm_hour * 3600;
 	tm->tm_min = time / 60;
 	tm->tm_sec = time - tm->tm_min * 60;
+
+	tm->tm_isdst = 0;
 }
 EXPORT_SYMBOL(rtc_time_to_tm);

-- 
1.7.3.1

--
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/