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SubjectRe: [patch V2 01/38] posix-cpu-timers: Provide task validation functions
On Thu, 22 Aug 2019, Frederic Weisbecker wrote:
> On Thu, Aug 22, 2019 at 12:33:56AM +0200, Frederic Weisbecker wrote:
> > On Wed, Aug 21, 2019 at 09:08:48PM +0200, Thomas Gleixner wrote:
> > > The code contains three slightly different copies of validating whether a
> > > given clock resolves to a valid task and whether the current caller has
> > > permissions to access it.
> > >
> > > Create central functions. Replace check_clock() as a first step and rename
> > > it to something sensible.
> > >
> > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > > ---
> > > kernel/time/posix-cpu-timers.c | 65 +++++++++++++++++++++++++++--------------
> > > 1 file changed, 44 insertions(+), 21 deletions(-)
> > >
> > > --- a/kernel/time/posix-cpu-timers.c
> > > +++ b/kernel/time/posix-cpu-timers.c
> > > @@ -35,27 +35,52 @@ void update_rlimit_cpu(struct task_struc
> > > spin_unlock_irq(&task->sighand->siglock);
> > > }
> > >
> > > -static int check_clock(const clockid_t which_clock)
> > > +/*
> > > + * Functions for validating access to tasks.
> > > + */
> > > +static struct task_struct *lookup_task(const pid_t pid, bool thread)
> > > {
> > > - int error = 0;
> > > struct task_struct *p;
> > > - const pid_t pid = CPUCLOCK_PID(which_clock);
> > >
> > > - if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
> > > - return -EINVAL;
> > > + if (!pid)
> > > + return thread ? current : current->group_leader;
> > >
> > > - if (pid == 0)
> > > - return 0;
> > > + p = find_task_by_vpid(pid);
> > > + if (!p || p == current)
> > > + return p;
> >
> > What if (p == current && !thread && !has_group_leader_pid(p)) ?
>
> Ah looking at the next patch, posix_cpu_clock_get_task() and posix_cpu_clock_getres()
> had different ad-hoc checks for this specific case.
>
> clock_getres() used to return -EINVAL while clock_get() doesn't
> care. They certainly should agree in their behaviour. I'm not sure which
> one is correct. It probably doesn't matter much.

Let me stare on the different variants again

Thanks,

tglx

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