Commit 3a879fb3 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

file: Implement task_lookup_fd_rcu 



As a companion to lookup_fd_rcu implement task_lookup_fd_rcu for
querying an arbitrary process about a specific file.

Acked-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
v1: https://lkml.kernel.org/r/20200818103713.aw46m7vprsy4vlve@wittgenstein
Link: https://lkml.kernel.org/r/20201120231441.29911-11-ebiederm@xmission.com


Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 460b4f81

fs/file.c

+15 −0
Original line number Diff line number Diff line
@@ -865,6 +865,21 @@ struct file *fget_task(struct task_struct *task, unsigned int fd) 
	return file;

}



struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)

{

	/* Must be called with rcu_read_lock held */

	struct files_struct *files;

	struct file *file = NULL;



	task_lock(task);

	files = task->files;

	if (files)

		file = files_lookup_fd_rcu(files, fd);

	task_unlock(task);



	return file;

}



/*

 * Lightweight file lookup - no refcnt increment if fd table isn't shared.

 *

include/linux/fdtable.h

+2 −0
Original line number Diff line number Diff line
@@ -110,6 +110,8 @@ static inline struct file *lookup_fd_rcu(unsigned int fd) 
	return files_lookup_fd_rcu(current->files, fd);

}



struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd);



struct task_struct;



struct files_struct *get_files_struct(struct task_struct *);