[Devel] [PATCH rh8] ve/time: Limit values to write in ve::clock_[monotonic|bootbased]

[Kirill Tkhai]

On 15.10.2020 14:10, Konstantin Khorenko wrote:
> What do we mean when write a valie XXX into, say, ve::ve.clock_bootbased?
> We mean that "up to now the CT worked for XXX secs/usecs already".
> And we store the delta between Node "now" and XXX into ve->start_time_real.
> 
> If the CT worked less than the current Node, ve->start_time_real will
> contain positive value and we'll substitute it from Node's "now" each
> time when we need to get the time since the CT start.
> 
> If the CT worked longer than the current CT (say, CT has been migrated
> from another HN), the stored delta will be negative and thus we'll "add"
> more time for Node's "now".
> 
> So then what do we want to limit?
> 1. Negative values written to ve::clock_[monotonic|bootbased].
>    Indeed we can hardly imagine that the CT has been started, but the
>    time since it's start is negative.
> 
> 2. A big positive value, so some time later when we read from
>    ve::clock_[monotonic|bootbased] we get an overflowed value.
> 
> Both these checks are performed by timespec_valid_strict().
> 
> Fixes: 25cab3041305 ("ve: Add interface for
> ve::clock_[monotonic|bootbased] adjustment")
> 
> Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>

Reviewed-by: Kirill Tkhai <ktkhai at virtuozzo.com>

> ---
>  kernel/ve/ve.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
> index cc26d3b2fa9b..43e37b27e887 100644
> --- a/kernel/ve/ve.c
> +++ b/kernel/ve/ve.c
> @@ -965,6 +965,8 @@ static ssize_t ve_ts_write(struct kernfs_open_file *of, char *buf,
>  
>  	if (sscanf(buf, "%ld %ld", &delta.tv_sec, &delta.tv_nsec) != 2)
>  		return -EINVAL;
> +	if (!timespec_valid_strict(&delta))
> +		return -EINVAL;
>  	delta_ns = timespec_to_ns(&delta);
>  
>  	switch (of_cft(of)->private) {
>