On Sat, 14 Dec 2019 at 09:46, Cornelia Huck <cohuck@redhat.com> wrote:
>
> The Posix implementation of guest-set-time invokes hwclock to
> set/retrieve the time to/from the hardware clock. If hwclock
> is not available, the user is currently informed that "hwclock
> failed to set hardware clock to system time", which is quite
> misleading. This may happen e.g. on s390x, which has a different
> timekeeping concept anyway.
>
> Let's check for the availability of the hwclock command and
> return QERR_UNSUPPORTED for guest-set-time if it is not available.
>
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> Message-Id: <20191205115350.18713-1-cohuck@redhat.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
> qga/commands-posix.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 1c1a165daed8..0be301a4ea77 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -156,6 +156,17 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
> pid_t pid;
> Error *local_err = NULL;
> struct timeval tv;
> + static const char hwclock_path[] = "/sbin/hwclock";
> + static int hwclock_available = -1;
> +
> + if (hwclock_available < 0) {
> + hwclock_available = (access(hwclock_path, X_OK) == 0);
> + }
> +
> + if (!hwclock_available) {
> + error_setg(errp, QERR_UNSUPPORTED);
> + return;
> + }
>
> /* If user has passed a time, validate and set it. */
> if (has_time) {
> @@ -195,7 +206,7 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
>
> /* Use '/sbin/hwclock -w' to set RTC from the system time,
> * or '/sbin/hwclock -s' to set the system time from RTC. */
> - execle("/sbin/hwclock", "hwclock", has_time ? "-w" : "-s",
> + execle(hwclock_path, "hwclock", has_time ? "-w" : "-s",
> NULL, environ);
> _exit(EXIT_FAILURE);
> } else if (pid < 0) {
> --
FWIW, Coverity thought this might be a time-of-check-time-of-use
bug based on our doing an access() check and then later doing
an execle(). This seems like a false positive to me, so I've
marked it as such (CID 1411029).
thanks
-- PMM