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posix-cpu-timers: Provide task validation functions 

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>
Link: https://lkml.kernel.org/r/20190821192919.326097175@linutronix.de
This commit is contained in:
Thomas Gleixner 2019-08-21 21:08:48 +02:00
parent a42e43c3de
commit 6ae40e3fdc
1 changed files with 44 additions and 21 deletions
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65
kernel/time/posix-cpu-timers.c
View File

@ -35,27 +35,52 @@ void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
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;
if (thread)
return same_thread_group(p, current) ? p : NULL;
if (p == current)
return p;
return has_group_leader_pid(p) ? p : NULL;
}
static struct task_struct *__get_task_for_clock(const clockid_t clock,
bool getref)
{
const bool thread = !!CPUCLOCK_PERTHREAD(clock);
const pid_t pid = CPUCLOCK_PID(clock);
struct task_struct *p;
if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
return NULL;
rcu_read_lock();
p = find_task_by_vpid(pid);
if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
same_thread_group(p, current) : has_group_leader_pid(p))) {
error = -EINVAL;
}
p = lookup_task(pid, thread);
if (p && getref)
get_task_struct(p);
rcu_read_unlock();
return p;
}
return error;
static inline struct task_struct *get_task_for_clock(const clockid_t clock)
{
return __get_task_for_clock(clock, true);
}
static inline int validate_clock_permissions(const clockid_t clock)
{
return __get_task_for_clock(clock, false) ? 0 : -EINVAL;
}
/*
@ -125,7 +150,8 @@ static inline u64 virt_ticks(struct task_struct *p)
static int
posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
{
int error = check_clock(which_clock);
int error = validate_clock_permissions(which_clock);
if (!error) {
tp->tv_sec = 0;
tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
@ -142,20 +168,17 @@ posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
}
static int
posix_cpu_clock_set(const clockid_t which_clock, const struct timespec64 *tp)
posix_cpu_clock_set(const clockid_t clock, const struct timespec64 *tp)
{
int error = validate_clock_permissions(clock);
/*
* You can never reset a CPU clock, but we check for other errors
* in the call before failing with EPERM.
*/
int error = check_clock(which_clock);
if (error == 0) {
error = -EPERM;
}
return error;
return error ? : -EPERM;
}
/*
* Sample a per-thread clock for the given task.
*/