Re: [PATCH] Read THREAD_CPUTIME clock from other processes.

[Oleg Nesterov]

On 01/07, Roland McGrath wrote:
>
> This can certainly be enhanced, but it opens some cans of worms about the
> security question.  It is probably still considered an unsafe information
> leak to let every process examine every other process's thread clocks.

Yes, I was worried about possible security issues too. But, it seems,
/proc/pid/task/tid/stat (do_task_stat) shows ->utime/stime anyway.
And /proc/schedstat shows sum_exec_runtime.

> I'll leave that judgement to security folks.

Agreed.

> As well as the information leak, it is most certainly a DoS attack vector
> to allow one process to set CPU timers an another process or its threads.

No, the suggested change doesn't go that far, afaics. It only modifies
check_clock: this affects clock_getres and clock_set (which does nothing),
and posix_cpu_clock_get: affects clock_gettime().

Oleg.

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