[PATCH 06/17] file: Implement fcheck_task

Eric W. Biederman
2020-08-17T22:10:30Z

As a companion to fget_task implement fcheck_task for use for querying
a process about a specific file.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
fs/file.c | 13 +++++++++++++
include/linux/fdtable.h | 1 +
2 files changed, 14 insertions(+)

diff --git a/fs/file.c b/fs/file.c
index c585dbaf31a3..8d4b385055e9 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -863,6 +863,19 @@ struct file *fget_task(struct task_struct *task, unsigned int fd)
return file;
}

+struct file *fcheck_task(struct task_struct *task, unsigned int fd)
+{
+ /* Must be called with rcu_read_lock held */
+ struct file *file = NULL;
+
+ task_lock(task);
+ if (task->files)
+ file = fcheck_files(task->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 7cc9885044d9..def9debd2ce2 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -103,6 +103,7 @@ static inline struct file *fcheck_files(struct files_struct *files, unsigned int
* Check whether the specified fd has an open file.
*/
#define fcheck(fd) fcheck_files(current->files, fd)
+struct file *fcheck_task(struct task_struct *task, unsigned int fd);

struct task_struct;

--
2.25.0