From: Chiawei Wang chiaweiwang@google.com
CLOCK_REALTIME in vdso data won't be updated if __arch_use_vsyscall() returns false. It will let time() return an incorrect time value. Since time() is designed to return the seconds since the Epoch, using CLOCK_REALTIME_COARSE can still fulfill the request and never fails.
Signed-off-by: Chiawei Wang chiaweiwang@google.com Signed-off-by: Mark Salyzyn salyzyn@android.com Cc: linux-kernel@vger.kernel.org Cc: kernel-team@android.com Cc: stable@vger.kernel.org # 5.4+ --- lib/vdso/gettimeofday.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c index a2909af4b924..7ea22096cbe2 100644 --- a/lib/vdso/gettimeofday.c +++ b/lib/vdso/gettimeofday.c @@ -324,7 +324,7 @@ __cvdso_time_data(const struct vdso_data *vd, __kernel_old_time_t *time) vd->clock_mode == VDSO_CLOCKMODE_TIMENS) vd = __arch_get_timens_vdso_data();
- t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec); + t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE].sec);
if (time) *time = t;
Mark Salyzyn salyzyn@android.com writes:
From: Chiawei Wang chiaweiwang@google.com
CLOCK_REALTIME in vdso data won't be updated if __arch_use_vsyscall() returns false.
Errm!
# git grep __arch_use_vsyscall #
Aside of that update_vsyscall() updates CLOCK_REALTIME data unconditionally. No idea what this patch is solving.
Cc: stable@vger.kernel.org # 5.4+
This # 5.4+ is pointless. You really want to add a fixes tag which pin points the commit which introduced the wreckage.
But thats moot as this is not fixing anything not even in 5.4.
I assume this was developed against some Frankenkernel which has a messy backport or a snapshot of some development version of that vdso stuff.
Not that I want to know, but please make sure that something you send my way makes sense on sane kernels.
Oh well.
Thanks,
tglx
On Jun 11, 2020, at 12:34 PM, Thomas Gleixner tglx@linutronix.de wrote:
Mark Salyzyn salyzyn@android.com writes:
From: Chiawei Wang chiaweiwang@google.com
CLOCK_REALTIME in vdso data won't be updated if __arch_use_vsyscall() returns false.
Errm!
# git grep __arch_use_vsyscall #
Aside of that update_vsyscall() updates CLOCK_REALTIME data unconditionally. No idea what this patch is solving.
Cc: stable@vger.kernel.org # 5.4+
This # 5.4+ is pointless. You really want to add a fixes tag which pin points the commit which introduced the wreckage.
But thats moot as this is not fixing anything not even in 5.4.
I assume this was developed against some Frankenkernel which has a messy backport or a snapshot of some development version of that vdso stuff.
Yes, problem code was removed with 52338415cf4d4064ae6b8dd972dadbda841da4fa not applied.
4.19 back port without time namespaces, chip vendor using __arch_use_vsyscall to solve a chip errata.
Not that I want to know, but please make sure that something you send my way makes sense on sane kernels.
Oh well.
Thanks,
tglx
Sorry for your troubles.
Sincerely — Mark Salyzyn
linux-stable-mirror@lists.linaro.org
-
Mark Salyzyn -
Thomas Gleixner