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  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]
Date:   Fri, 14 Aug 2020 19:17:30 +1000
From:   Victor Ding <>
To:     LKML <>
Cc:     Alexandre Belloni <>,
        Victor Ding <>,
        Alessandro Zummo <>,
Subject: [PATCH v2] rtc: cmos: zero-init wkalrm when reading from CMOS

cmos_read_alarm() may leave certain fields of a struct rtc_wkalrm
untouched; therefore, these fields contain garbage if not properly
initialized, leading to inconsistent values when converting into
time64_t. This patch to zero initialize the struct before calling

Note that this patch is not intended to produce a correct time64_t, it
is only to produce a consistent value. In the case of suspend/resume, a
correct time64_t is not necessary; a consistent value is sufficient to
correctly perform an equality test for t_current_expires and
t_saved_expires. Logic to deduce a correct time64_t is expensive and
hence should be avoided.

Signed-off-by: Victor Ding <>

Changes in v2:
    - Initialize the struct to 0 instead of -1;
    - Initialize the whole struct rtc_wkalrm.

 drivers/rtc/rtc-cmos.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index bcc96ab7793f..c633319cdb91 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -1006,6 +1006,7 @@ static int cmos_suspend(struct device *dev)
+	memset(&cmos->saved_wkalrm, 0, sizeof(struct rtc_wkalrm));
 	cmos_read_alarm(dev, &cmos->saved_wkalrm);
 	dev_dbg(dev, "suspend%s, ctrl %02x\n",
@@ -1054,6 +1055,7 @@ static void cmos_check_wkalrm(struct device *dev)
+	memset(&current_alarm, 0, sizeof(struct rtc_wkalrm));
 	cmos_read_alarm(dev, &current_alarm);
 	t_current_expires = rtc_tm_to_time64(&current_alarm.time);
 	t_saved_expires = rtc_tm_to_time64(&cmos->saved_wkalrm.time);

Powered by blists - more mailing lists