As a companion to lookup_fd_rcu implement task_lookup_fd_rcu for querying an arbitrary process about a specific file. Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx> v1: https://lkml.kernel.org/r/20200818103713.aw46m7vprsy4vlve@wittgenstein Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> --- fs/file.c | 15 +++++++++++++++ include/linux/fdtable.h | 2 ++ 2 files changed, 17 insertions(+) diff --git a/fs/file.c b/fs/file.c index 5861c4f89419..6448523ca29e 100644 --- a/fs/file.c +++ b/fs/file.c @@ -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. * diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 2a4a8fed536e..a0558ae9b40c 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -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 *); -- 2.25.0
