linux-kernel - [PATCH 1/3] s390/vdso: fix tod clock steering

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: <20210323215819.4161164-2-hca@linux.ibm.com>
Date:   Tue, 23 Mar 2021 22:58:17 +0100
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Li Wang <liwang@...hat.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     ltp@...ts.linux.it, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org
Subject: [PATCH 1/3] s390/vdso: fix tod clock steering

The s390 specific vdso function __arch_get_hw_counter() is supposed to
consider tod clock steering.

If a tod clock steering event happens and the tod clock is set to a
new value __arch_get_hw_counter() will not return the real tod clock
value but slowly drift it from the old delta until the returned value
finally matches the real tod clock value again.

When converting the assembler code to C it was forgotten to tell user
space in which direction the clock has to be adjusted.

Worst case is now that instead of drifting the clock slowly it will
jump into the opposite direction by a factor of two.

Fix this by simply providing the missing value to user space.

Fixes: 4bff8cb54502 ("s390: convert to GENERIC_VDSO")
Cc: <stable@...r.kernel.org> # 5.10
Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>
---
 arch/s390/kernel/time.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 165da961f901..e37285a5101b 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -382,6 +382,7 @@ static void clock_sync_global(unsigned long delta)
 		      tod_steering_delta);
 	tod_steering_end = now + (abs(tod_steering_delta) << 15);
 	vdso_data->arch_data.tod_steering_end = tod_steering_end;
+	vdso_data->arch_data.tod_steering_delta = tod_steering_delta;

 	/* Update LPAR offset. */
 	if (ptff_query(PTFF_QTO) && ptff(&qto, sizeof(qto), PTFF_QTO) == 0)
-- 
2.25.1