[patch V2 5/6] posix-cpu-timers: Return PTR_ERR() from lookup_task()

[Thomas Gleixner]

To prepare for changing the return code to -EPERM when the ptrace
permission check fails, use PTR_ERR() to return the error information from
lookup_task() and fixup all call sites.

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
V2: New patch
---
 kernel/time/posix-cpu-timers.c |   22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -63,7 +63,7 @@ static struct task_struct *lookup_task(c
 
        p = find_task_by_vpid(pid);
        if (!p)
-               return p;
+               return ERR_PTR(-EINVAL);
 
        if (gettime) {
                /*
@@ -103,11 +103,11 @@ static struct task_struct *lookup_task(c
                 * the timer is destroyed.
                 */
                if (!has_group_leader_pid(p))
-                       return NULL;
+                       return ERR_PTR(-EINVAL);
        }
 
        /* Decide based on the ptrace permissions. */
-       return ptrace_may_access(p, mode) ? p : NULL;
+       return ptrace_may_access(p, mode) ? p : ERR_PTR(-EINVAL);
 }
 
 static struct task_struct *__get_task_for_clock(const clockid_t clock,
@@ -118,11 +118,11 @@ static struct task_struct *__get_task_fo
        struct task_struct *p;
 
        if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
-               return NULL;
+               return ERR_PTR(-EINVAL);
 
        rcu_read_lock();
        p = lookup_task(pid, thread, gettime);
-       if (p && getref)
+       if (!IS_ERR(p) && getref)
                get_task_struct(p);
        rcu_read_unlock();
        return p;
@@ -140,7 +140,9 @@ static inline struct task_struct *get_ta
 
 static inline int validate_clock_permissions(const clockid_t clock)
 {
-       return __get_task_for_clock(clock, false, false) ? 0 : -EINVAL;
+       struct task_struct *res =  __get_task_for_clock(clock, false, false);
+
+       return IS_ERR(res) ? PTR_ERR(res) : 0;
 }
 
 /*
@@ -391,8 +393,8 @@ static int posix_cpu_clock_get(const clo
        u64 t;
 
        tsk = get_task_for_clock_get(clock);
-       if (!tsk)
-               return -EINVAL;
+       if (IS_ERR(tsk))
+               return PTR_ERR(tsk);
 
        if (CPUCLOCK_PERTHREAD(clock))
                t = cpu_clock_sample(clkid, tsk);
@@ -413,8 +415,8 @@ static int posix_cpu_timer_create(struct
 {
        struct task_struct *p = get_task_for_clock(new_timer->it_clock);
 
-       if (!p)
-               return -EINVAL;
+       if (IS_ERR(p))
+               return PTR_ERR(p);
 
        new_timer->kclock = &clock_posix_cpu;
        timerqueue_init(&new_timer->it.cpu.node);