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05 April 2024, 19:05:47 UTC
Revision b99328a60a482108f5195b4d611f90992ca016ba authored by Thomas Gleixner on 22 August 2019, 11:00:15 UTC, committed by Thomas Gleixner on 23 August 2019, 00:12:11 UTC 
timekeeping/vsyscall: Prevent math overflow in BOOTTIME update
 
The VDSO update for CLOCK_BOOTTIME has a overflow issue as it shifts the
nanoseconds based boot time offset left by the clocksource shift. That
overflows once the boot time offset becomes large enough. As a consequence
CLOCK_BOOTTIME in the VDSO becomes a random number causing applications to
misbehave.

Fix it by storing a timespec64 representation of the offset when boot time
is adjusted and add that to the MONOTONIC base time value in the vdso data
page. Using the timespec64 representation avoids a 64bit division in the
update code.

Fixes: 44f57d788e7d ("timekeeping: Provide a generic update_vsyscall() implementation")
Reported-by: Chris Clayton <chris2553@googlemail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Chris Clayton <chris2553@googlemail.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908221257580.1983@nanos.tec.linutronix.de
1 parent 59c36bc
History
Tip revision: b99328a60a482108f5195b4d611f90992ca016ba authored by Thomas Gleixner on 22 August 2019, 11:00:15 UTC
timekeeping/vsyscall: Prevent math overflow in BOOTTIME update
Tip revision: b99328a
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