lkml.org 
[lkml]   [2019]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch V2 01/38] posix-cpu-timers: Provide task validation functions
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.

\
 
 \ /
  Last update: 2019-08-22 01:05    [W:0.095 / U:1.712 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site