On Wed, Jun 26, 2019 at 04:07:33PM +0200, Christian Brauner wrote: > Hi Linus, > > This pull request removes the validation of the pidfd return argument if > CLONE_PIDFD is specified: > > The following changes since commit 4b972a01a7da614b4796475f933094751a295a2f: > > Linux 5.2-rc6 (2019-06-22 16:01:36 -0700) > > are available in the Git repository at: > > g...@gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux > tags/for-linus-20190626 > > for you to fetch changes up to bee19cd8f241ab3cd1bf79e03884e5371f9ef514: > > samples: make pidfd-metadata fail gracefully on older kernels (2019-06-24 > 15:55:50 +0200) > > Userspace tools and libraries such as strace or glibc need a cheap and > reliable way to tell whether CLONE_PIDFD is supported. > The easiest way is to pass an invalid fd value in the return argument, > perform the syscall and verify the value in the return argument has been > changed to a valid fd. > > However, if CLONE_PIDFD is specified we currently check if pidfd == 0 and > return EINVAL if not. > > The check for pidfd == 0 was originally added to enable us to abuse the > return argument for passing additional flags along with CLONE_PIDFD in the > future. > > However, extending legacy clone this way would be a terrible idea and with > clone3 on the horizon and the ability to reuse CLONE_DETACHED with > CLONE_PIDFD there's no real need for this clutch. So remove the pidfd == 0 > check and help userspace out. > > Please consider pulling these changes from the signed for-linus-20190626 tag.
Al has another patch that removes the use of anon_inode_getfd() for the sake of anon_inode_getfile() + fd_install() to avoid the use of ksys_close(). I'll put it in my fixes branch and send a new PR with all those fixes in a few hours. Thanks! Christian
