From: Kees Cook <keescook@chromium.org>
To: Tycho Andersen <tycho@tycho.ws>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux Containers <containers@lists.linux-foundation.org>,
Linux API <linux-api@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Oleg Nesterov <oleg@redhat.com>,
"Eric W . Biederman" <ebiederm@xmission.com>,
"Serge E . Hallyn" <serge@hallyn.com>,
Christian Brauner <christian.brauner@ubuntu.com>,
Tyler Hicks <tyhicks@canonical.com>,
Akihiro Suda <suda.akihiro@lab.ntt.co.jp>,
Jann Horn <jannh@google.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v7 4/6] files: add a replace_fd_files() function
Date: Thu, 27 Sep 2018 14:59:53 -0700 [thread overview]
Message-ID: <CAGXu5jLOe0izpGoB8c-hAeH2SzA51dF1BuMcXbk-d=QwqfjxxQ@mail.gmail.com> (raw)
In-Reply-To: <20180927151119.9989-5-tycho@tycho.ws>
On Thu, Sep 27, 2018 at 8:11 AM, Tycho Andersen <tycho@tycho.ws> wrote:
> Similar to fd_install/__fd_install, we want to be able to replace an fd of
> an arbitrary struct files_struct, not just current's. We'll use this in the
> next patch to implement the seccomp ioctl that allows inserting fds into a
> stopped process' context.
>
> v7: new in v7
>
> Signed-off-by: Tycho Andersen <tycho@tycho.ws>
> CC: Alexander Viro <viro@zeniv.linux.org.uk>
> CC: Kees Cook <keescook@chromium.org>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Eric W. Biederman <ebiederm@xmission.com>
> CC: "Serge E. Hallyn" <serge@hallyn.com>
> CC: Christian Brauner <christian.brauner@ubuntu.com>
> CC: Tyler Hicks <tyhicks@canonical.com>
> CC: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
> ---
> fs/file.c | 22 +++++++++++++++-------
> include/linux/file.h | 8 ++++++++
> 2 files changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/fs/file.c b/fs/file.c
> index 7ffd6e9d103d..3b3c5aadaadb 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -850,24 +850,32 @@ __releases(&files->file_lock)
> }
>
> int replace_fd(unsigned fd, struct file *file, unsigned flags)
> +{
> + return replace_fd_task(current, fd, file, flags);
> +}
> +
> +/*
> + * Same warning as __alloc_fd()/__fd_install() here.
> + */
> +int replace_fd_task(struct task_struct *task, unsigned fd,
> + struct file *file, unsigned flags)
> {
> int err;
> - struct files_struct *files = current->files;
Same feedback as Jann: on a purely "smaller diff" note, this could
just be s/current/task/ here and all the other s/files/task->files/
would go away...
>
> if (!file)
> - return __close_fd(files, fd);
> + return __close_fd(task->files, fd);
>
> - if (fd >= rlimit(RLIMIT_NOFILE))
> + if (fd >= task_rlimit(task, RLIMIT_NOFILE))
> return -EBADF;
>
> - spin_lock(&files->file_lock);
> - err = expand_files(files, fd);
> + spin_lock(&task->files->file_lock);
> + err = expand_files(task->files, fd);
> if (unlikely(err < 0))
> goto out_unlock;
> - return do_dup2(files, file, fd, flags);
> + return do_dup2(task->files, file, fd, flags);
>
> out_unlock:
> - spin_unlock(&files->file_lock);
> + spin_unlock(&task->files->file_lock);
> return err;
> }
>
> diff --git a/include/linux/file.h b/include/linux/file.h
> index 6b2fb032416c..f94277fee038 100644
> --- a/include/linux/file.h
> +++ b/include/linux/file.h
> @@ -11,6 +11,7 @@
> #include <linux/posix_types.h>
>
> struct file;
> +struct task_struct;
>
> extern void fput(struct file *);
>
> @@ -79,6 +80,13 @@ static inline void fdput_pos(struct fd f)
>
> extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);
> extern int replace_fd(unsigned fd, struct file *file, unsigned flags);
> +/*
> + * Warning! This is only safe if you know the owner of the files_struct is
> + * stopped outside syscall context. It's a very bad idea to use this unless you
> + * have similar guarantees in your code.
> + */
> +extern int replace_fd_task(struct task_struct *task, unsigned fd,
> + struct file *file, unsigned flags);
Perhaps call this __replace_fd() to indicate the "please don't use
this unless you're very sure"ness of it?
> extern void set_close_on_exec(unsigned int fd, int flag);
> extern bool get_close_on_exec(unsigned int fd);
> extern int get_unused_fd_flags(unsigned flags);
> --
> 2.17.1
>
If I can get an Ack from Al, that would be very nice. :)
-Kees
--
Kees Cook
Pixel Security
next prev parent reply other threads:[~2018-09-28 4:20 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-27 15:11 [PATCH v7 0/6] seccomp trap to userspace Tycho Andersen
2018-09-27 15:11 ` [PATCH v7 1/6] seccomp: add a return code to " Tycho Andersen
2018-09-27 21:31 ` Kees Cook
2018-09-27 22:48 ` Tycho Andersen
2018-09-27 23:10 ` Kees Cook
2018-09-28 14:39 ` Tycho Andersen
2018-10-08 14:58 ` Christian Brauner
2018-10-09 14:28 ` Tycho Andersen
2018-10-09 16:24 ` Christian Brauner
2018-10-09 16:29 ` Tycho Andersen
2018-10-17 20:29 ` Tycho Andersen
2018-10-17 22:21 ` Kees Cook
2018-10-17 22:33 ` Tycho Andersen
2018-10-21 16:04 ` Tycho Andersen
2018-10-22 9:42 ` Christian Brauner
2018-09-27 21:51 ` Jann Horn
2018-09-27 22:45 ` Kees Cook
2018-09-27 23:08 ` Tycho Andersen
2018-09-27 23:04 ` Tycho Andersen
2018-09-27 23:37 ` Jann Horn
2018-09-29 0:28 ` Aleksa Sarai
2018-09-27 15:11 ` [PATCH v7 2/6] seccomp: make get_nth_filter available outside of CHECKPOINT_RESTORE Tycho Andersen
2018-09-27 16:51 ` Jann Horn
2018-09-27 21:42 ` Kees Cook
2018-10-08 13:55 ` Christian Brauner
2018-09-27 15:11 ` [PATCH v7 3/6] seccomp: add a way to get a listener fd from ptrace Tycho Andersen
2018-09-27 16:20 ` Jann Horn
2018-09-27 16:34 ` Tycho Andersen
2018-09-27 17:35 ` Jann Horn
2018-09-27 18:09 ` Tycho Andersen
2018-09-27 21:53 ` Kees Cook
2018-10-08 15:16 ` Christian Brauner
2018-10-08 15:33 ` Jann Horn
2018-10-08 16:21 ` Christian Brauner
2018-10-08 16:42 ` Jann Horn
2018-10-08 18:18 ` Christian Brauner
2018-10-09 12:39 ` Jann Horn
2018-10-09 13:28 ` Christian Brauner
2018-10-09 13:36 ` Jann Horn
2018-10-09 13:49 ` Christian Brauner
2018-10-09 13:50 ` Jann Horn
2018-10-09 14:09 ` Christian Brauner
2018-10-09 15:26 ` Jann Horn
2018-10-09 16:20 ` Christian Brauner
2018-10-09 16:26 ` Jann Horn
2018-10-10 12:54 ` Christian Brauner
2018-10-10 13:09 ` Christian Brauner
2018-10-10 13:10 ` Jann Horn
2018-10-10 13:18 ` Christian Brauner
2018-10-10 15:31 ` Paul Moore
2018-10-10 15:33 ` Jann Horn
2018-10-10 15:39 ` Christian Brauner
2018-10-10 16:54 ` Tycho Andersen
2018-10-10 17:15 ` Christian Brauner
2018-10-10 17:26 ` Tycho Andersen
2018-10-10 18:28 ` Christian Brauner
2018-10-11 7:24 ` Paul Moore
2018-10-11 13:39 ` Jann Horn
2018-10-11 23:10 ` Paul Moore
2018-10-12 1:02 ` Andy Lutomirski
2018-10-12 20:02 ` Tycho Andersen
2018-10-12 20:06 ` Jann Horn
2018-10-12 20:11 ` Christian Brauner
2018-10-08 18:00 ` Tycho Andersen
2018-10-08 18:41 ` Christian Brauner
2018-10-10 17:45 ` Andy Lutomirski
2018-10-10 18:26 ` Christian Brauner
2018-09-27 15:11 ` [PATCH v7 4/6] files: add a replace_fd_files() function Tycho Andersen
2018-09-27 16:49 ` Jann Horn
2018-09-27 18:04 ` Tycho Andersen
2018-09-27 21:59 ` Kees Cook [this message]
2018-09-28 2:20 ` Kees Cook
2018-09-28 2:46 ` Jann Horn
2018-09-28 5:23 ` Tycho Andersen
2018-09-27 15:11 ` [PATCH v7 5/6] seccomp: add a way to pass FDs via a notification fd Tycho Andersen
2018-09-27 16:39 ` Jann Horn
2018-09-27 22:13 ` Tycho Andersen
2018-09-27 19:28 ` Jann Horn
2018-09-27 22:14 ` Tycho Andersen
2018-09-27 22:17 ` Jann Horn
2018-09-27 22:49 ` Tycho Andersen
2018-09-27 22:09 ` Kees Cook
2018-09-27 22:15 ` Tycho Andersen
2018-09-27 15:11 ` [PATCH v7 6/6] samples: add an example of seccomp user trap Tycho Andersen
2018-09-27 22:11 ` Kees Cook
2018-09-28 21:57 ` [PATCH v7 0/6] seccomp trap to userspace Michael Kerrisk (man-opages)
2018-09-28 22:03 ` Tycho Andersen
2018-09-28 22:16 ` Michael Kerrisk (man-pages)
2018-09-28 22:34 ` Kees Cook
2018-09-28 22:46 ` Michael Kerrisk (man-pages)
2018-09-28 22:48 ` Jann Horn
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