diff options
| author | Boris Ostrovsky <boris.ostrovsky@oracle.com> | 2014-05-09 11:11:27 -0400 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2014-05-09 08:45:52 -0700 |
| commit | 28b92e09e25bdc0ae864b22eacf195a74f861389 (patch) | |
| tree | 2483505e3c98fd83565a1576af11daf629f8efdf | |
| parent | c45f77364ba060395b7eff1bf45e6c537f913380 (diff) | |
x86, vdso, time: Cast tv_nsec to u64 for proper shifting in update_vsyscall()
With tk->wall_to_monotonic.tv_nsec being a 32-bit value on 32-bit
systems, (tk->wall_to_monotonic.tv_nsec << tk->shift) in update_vsyscall()
may lose upper bits or, worse, add them since compiler will do this:
(u64)(tk->wall_to_monotonic.tv_nsec << tk->shift)
instead of
((u64)tk->wall_to_monotonic.tv_nsec << tk->shift)
So if, for example, tv_nsec is 0x800000 and shift is 8 we will end up
with 0xffffffff80000000 instead of 0x80000000. And then we are stuck in
the subsequent 'while' loop.
We need an explicit cast.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: http://lkml.kernel.org/r/1399648287-15178-1-git-send-email-boris.ostrovsky@oracle.com
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: <stable@vger.kernel.org> # v3.14
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
| -rw-r--r-- | arch/x86/kernel/vsyscall_gtod.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/vsyscall_gtod.c b/arch/x86/kernel/vsyscall_gtod.c index f9c6e56e14b5..9531fbb123ba 100644 --- a/arch/x86/kernel/vsyscall_gtod.c +++ b/arch/x86/kernel/vsyscall_gtod.c @@ -43,7 +43,7 @@ void update_vsyscall(struct timekeeper *tk) vdata->monotonic_time_sec = tk->xtime_sec + tk->wall_to_monotonic.tv_sec; vdata->monotonic_time_snsec = tk->xtime_nsec - + (tk->wall_to_monotonic.tv_nsec + + ((u64)tk->wall_to_monotonic.tv_nsec << tk->shift); while (vdata->monotonic_time_snsec >= (((u64)NSEC_PER_SEC) << tk->shift)) { |