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Date: Fri, 20 Nov 2020 17:14:28 -0600 From: "Eric W. Biederman" <ebiederm@...ssion.com> To: linux-kernel@...r.kernel.org Cc: linux-fsdevel@...r.kernel.org, criu@...nvz.org, bpf@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <christian.brauner@...ntu.com>, Oleg Nesterov <oleg@...hat.com>, Cyrill Gorcunov <gorcunov@...il.com>, Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>, Daniel P . Berrangé <berrange@...hat.com>, Jeff Layton <jlayton@...hat.com>, Miklos Szeredi <miklos@...redi.hu>, Matthew Wilcox <willy@...radead.org>, "J. Bruce Fields" <bfields@...ldses.org>, Trond Myklebust <trond.myklebust@...merspace.com>, Chris Wright <chrisw@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, "Eric W. Biederman" <ebiederm@...ssion.com> Subject: [PATCH v2 11/24] 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: Christian Brauner <christian.brauner@...ntu.com> v1: https://lkml.kernel.org/r/20200818103713.aw46m7vprsy4vlve@wittgenstein Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com> --- 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
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