kcmp: In get_file_raw_ptr use task_lookup_fd_rcu

Modify get_file_raw_ptr to use task_lookup_fd_rcu.  The helper
task_lookup_fd_rcu does the work of taking the task lock and verifying
that task->files != NULL and then calls files_lookup_fd_rcu.  So let
use the helper to make a simpler implementation of get_file_raw_ptr.

Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Link: https://lkml.kernel.org/r/20201120231441.29911-13-ebiederm@xmission.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

diff --git a/kernel/kcmp.c b/kernel/kcmp.c
index 990717c..36e58eb 100644 (file)
--- a/kernel/kcmp.c
+++ b/kernel/kcmp.c
@@ -61,16 +61,11 @@ static int kcmp_ptr(void *v1, void *v2, enum kcmp_type type)
 static struct file *
 get_file_raw_ptr(struct task_struct *task, unsigned int idx)
 {
-       struct file *file = NULL;
+       struct file *file;
 
-       task_lock(task);
        rcu_read_lock();
-
-       if (task->files)
-               file = files_lookup_fd_rcu(task->files, idx);
-
+       file = task_lookup_fd_rcu(task, idx);
        rcu_read_unlock();
-       task_unlock(task);
 
        return file;
 }