Re: [PATCH v6 01/10] file: Export receive_fd() to modules

On Wed, Mar 31, 2021 at 04:05:10PM +0800, Xie Yongji wrote:

quoted

Export receive_fd() so that some modules can use
it to pass file descriptor between processes without
missing any security stuffs.

Signed-off-by: Xie Yongji <redacted>
---

Yeah, as I said in the other mail I'd be comfortable with exposing just
this variant of the helper.
Maybe this should be a separate patch bundled together with Christoph's
patch to split parts of receive_fd() into a separate helper.
This would also allow us to simplify a few other codepaths in drivers as
well btw. I just took a hasty stab at two of them:

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index c119736ca56a..3c716bf6d84b 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c

@@ -3728,8 +3728,9 @@ 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);

+               fd = receive_fd(fixup->file, O_CLOEXEC);
                if (fd < 0) {
                        binder_debug(BINDER_DEBUG_TRANSACTION,
                                     "failed fd fixup txn %d fd %d\n",