From: Yongji Xie <xieyongji@bytedance.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
Christoph Hellwig <hch@infradead.org>,
arve@android.com, tkjos@android.com, maco@android.com,
joel@joelfernandes.org, hridya@google.com, surenb@google.com,
viro@zeniv.linux.org.uk, sargun@sargun.me, keescook@chromium.org,
Jason Wang <jasowang@redhat.com>,
devel@driverdev.osuosl.org, linux-fsdevel@vger.kernel.org
Subject: Re: Re: [PATCH 2/2] binder: Use receive_fd() to receive file from another process
Date: Thu, 1 Apr 2021 19:11:27 +0800 [thread overview]
Message-ID: <CACycT3v3b7sfswm5Og9Pk-Q=FTD_RabTudv3TkHqo8fdSQvsXA@mail.gmail.com> (raw)
In-Reply-To: <20210401104034.52qaaoea27htkpbh@wittgenstein>
On Thu, Apr 1, 2021 at 6:40 PM Christian Brauner
<christian.brauner@ubuntu.com> wrote:
>
> On Thu, Apr 01, 2021 at 11:54:45AM +0200, Greg KH wrote:
> > On Thu, Apr 01, 2021 at 05:09:32PM +0800, Xie Yongji wrote:
> > > Use receive_fd() to receive file from another process instead of
> > > combination of get_unused_fd_flags() and fd_install(). This simplifies
> > > the logic and also makes sure we don't miss any security stuff.
> >
> > But no logic is simplified here, and nothing is "missed", so I do not
> > understand this change at all.
> >
> > >
> > > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > > ---
> > > drivers/android/binder.c | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> > > index c119736ca56a..080bcab7d632 100644
> > > --- a/drivers/android/binder.c
> > > +++ b/drivers/android/binder.c
> > > @@ -3728,7 +3728,7 @@ static int binder_apply_fd_fixups(struct binder_proc *proc,
> > > int ret = 0;
> > >
> > > list_for_each_entry(fixup, &t->fd_fixups, fixup_entry) {
> > > - int fd = get_unused_fd_flags(O_CLOEXEC);
> > > + int fd = receive_fd(fixup->file, O_CLOEXEC);
> >
> > Why 2 spaces?
> >
> > >
> > > if (fd < 0) {
> > > binder_debug(BINDER_DEBUG_TRANSACTION,
> > > @@ -3741,7 +3741,7 @@ static int binder_apply_fd_fixups(struct binder_proc *proc,
> > > "fd fixup txn %d fd %d\n",
> > > t->debug_id, fd);
> > > trace_binder_transaction_fd_recv(t, fd, fixup->offset);
> > > - fd_install(fd, fixup->file);
> > > + fput(fixup->file);
> >
> > Are you sure this is the same???
> >
> > I d onot understand the need for this change at all, what is wrong with
> > the existing code here?
>
> I suggested something like this.
> Some time back we added receive_fd() for seccomp and SCM_RIGHTS to have
> a unified way of installing file descriptors including taking care of
> handling sockets and running security hooks. The helper also encompasses
> the whole get_unused_fd() + fd_install dance.
> My suggestion was to look at all the places were we currently open-code
> this in drivers/:
>
Sorry for not following your suggestion. Yes, I looked at those
places. But I found that we will add security_file_receive()
implicitly if we replace get_unused_fd() + fd_install() with
receive_fd() for most drivers. Not sure if there will be some
regression. So I only do that where I think security_file_receive() is
needed, that is this patch. Although it looks like this is not a good
idea now...
Thanks,
Yongji
next prev parent reply other threads:[~2021-04-01 11:12 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 9:09 [PATCH 0/2] Export receive_fd() to modules and do some cleanups Xie Yongji
2021-04-01 9:09 ` [PATCH 1/2] file: Export receive_fd() to modules Xie Yongji
2021-04-01 9:52 ` Greg KH
2021-04-01 10:24 ` Yongji Xie
2021-04-01 9:09 ` [PATCH 2/2] binder: Use receive_fd() to receive file from another process Xie Yongji
2021-04-01 9:54 ` Greg KH
2021-04-01 10:12 ` Yongji Xie
2021-04-01 10:42 ` Greg KH
2021-04-01 11:29 ` Yongji Xie
2021-04-01 11:33 ` Greg KH
2021-04-01 12:28 ` Yongji Xie
2021-04-01 14:09 ` Greg KH
2021-04-02 9:12 ` Kees Cook
2021-04-01 10:40 ` Christian Brauner
2021-04-01 11:11 ` Yongji Xie [this message]
2021-04-16 5:19 ` Al Viro
2021-04-16 5:55 ` Al Viro
2021-04-16 13:42 ` Christian Brauner
2021-04-16 14:09 ` Al Viro
2021-04-16 15:13 ` Christian Brauner
2021-04-16 15:35 ` Al Viro
2021-04-16 15:58 ` Christian Brauner
2021-04-16 16:00 ` Christian Brauner
2021-04-16 17:00 ` Al Viro
2021-04-16 17:30 ` Al Viro
2021-04-17 1:30 ` Al Viro
2021-04-01 9:53 ` [PATCH 0/2] Export receive_fd() to modules and do some cleanups Greg KH
2021-04-01 10:00 ` Yongji Xie
2021-04-01 10:20 ` Christian Brauner
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