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SubjectRe: [patch V2 01/38] posix-cpu-timers: Provide task validation functions
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)) ?

> + if (thread)
> + return same_thread_group(p, current) ? p : NULL;
> + if (p == current)
> + return p;

You already checked that above.

> + return has_group_leader_pid(p) ? p : NULL;
> +}

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