Re: [patch 4/6] posix-cpu-timers: Restrict clock_gettime() permissions

Frederic Weisbecker
2019-09-23T13:39:11Z

On Thu, Sep 05, 2019 at 02:03:43PM +0200, Thomas Gleixner wrote:
> Similar to creating timers on a process there is no restriction at all to
> read the Posix CPU clocks of any process in the system. Per thread CPU
> clock access is limited to threads in the same thread group.
>
> The per process CPU clocks can be used to observe activity of tasks and
> reading them can affect the execution of the process to which they are
> attached as reading can require to lock sighand lock and sum up the fine
> grained accounting for all threads in the process.
>
> Restrict it by checking ptrace MODE_READ permissions of the reader on the
> target process.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>