linux-kernel - [PATCH AUTOSEL for 3.18 059/102] rtc: interface: Validate alarm-time before handling rollover

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]

Message-ID: <20180319161117.17833-59-alexander.levin@microsoft.com>
Date:   Mon, 19 Mar 2018 16:12:43 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 3.18 059/102] rtc: interface: Validate alarm-time
 before handling rollover

From: Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>

[ Upstream commit da96aea0ed177105cb13ee83b328f6c61e061d3f ]

In function __rtc_read_alarm() its possible for an alarm time-stamp to
be invalid even after replacing missing components with current
time-stamp. The condition 'alarm->time.tm_year < 70' will trigger this
case and will cause the call to 'rtc_tm_to_time64(&alarm->time)'
return a negative value for variable t_alm.

While handling alarm rollover this negative t_alm (assumed to seconds
offset from '1970-01-01 00:00:00') is converted back to rtc_time via
rtc_time64_to_tm() which results in this error log with seemingly
garbage values:

"rtc rtc0: invalid alarm value: -2-1--1041528741
2005511117:71582844:32"

This error was generated when the rtc driver (rtc-opal in this case)
returned an alarm time-stamp of '00-00-00 00:00:00' to indicate that
the alarm is disabled. Though I have submitted a separate fix for the
rtc-opal driver, this issue may potentially impact other
existing/future rtc drivers.

To fix this issue the patch validates the alarm time-stamp just after
filling up the missing datetime components and if rtc_valid_tm() still
reports it to be invalid then bails out of the function without
handling the rollover.

Reported-by: Steve Best <sbest@...hat.com>
Signed-off-by: Vaibhav Jain <vaibhav@...ux.vnet.ibm.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/rtc/interface.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 5b2717f5dafa..d4153892c120 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -249,6 +249,13 @@ int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 			missing = year;
 	}
 
+	/* Can't proceed if alarm is still invalid after replacing
+	 * missing fields.
+	 */
+	err = rtc_valid_tm(&alarm->time);
+	if (err)
+		goto done;
+
 	/* with luck, no rollover is needed */
 	rtc_tm_to_time(&now, &t_now);
 	rtc_tm_to_time(&alarm->time, &t_alm);
@@ -300,9 +307,9 @@ int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm)
 		dev_warn(&rtc->dev, "alarm rollover not handled\n");
 	}
 
-done:
 	err = rtc_valid_tm(&alarm->time);
 
+done:
 	if (err) {
 		dev_warn(&rtc->dev, "invalid alarm value: %d-%d-%d %d:%d:%d\n",
 			alarm->time.tm_year + 1900, alarm->time.tm_mon + 1,
-- 
2.14.1