Unverified Commit 232590ea authored by Christian Brauner's avatar Christian Brauner
Browse files

Revert "pidfd: prevent creation of pidfds for kthreads" 



This reverts commit 3b5bbe79.

Eric reported that systemd-shutdown gets broken by blocking the creating
of pidfds for kthreads as older versions seems to rely on being able to
create a pidfd for any process in /proc.

Reported-by: default avatarEric Biggers <ebiggers@kernel.org>
Link: https://lore.kernel.org/r/20240818035818.GA1929@sol.localdomain


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 524b2c6d

kernel/fork.c

+3 −22
Original line number Diff line number Diff line
@@ -2053,24 +2053,11 @@ static int __pidfd_prepare(struct pid *pid, unsigned int flags, struct file **re 
 */

int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret)

{

	if (!pid)

		return -EINVAL;



	scoped_guard(rcu) {

		struct task_struct *tsk;

	bool thread = flags & PIDFD_THREAD;



		if (flags & PIDFD_THREAD)

			tsk = pid_task(pid, PIDTYPE_PID);

		else

			tsk = pid_task(pid, PIDTYPE_TGID);

		if (!tsk)

	if (!pid || !pid_has_task(pid, thread ? PIDTYPE_PID : PIDTYPE_TGID))

		return -EINVAL;



		/* Don't create pidfds for kernel threads for now. */

		if (tsk->flags & PF_KTHREAD)

			return -EINVAL;

	}



	return __pidfd_prepare(pid, flags, ret);

}
@@ -2416,12 +2403,6 @@ __latent_entropy struct task_struct *copy_process( 
	if (clone_flags & CLONE_PIDFD) {

		int flags = (clone_flags & CLONE_THREAD) ? PIDFD_THREAD : 0;



		/* Don't create pidfds for kernel threads for now. */

		if (args->kthread) {

			retval = -EINVAL;

			goto bad_fork_free_pid;

		}



		/* Note that no task has been attached to @pid yet. */

		retval = __pidfd_prepare(pid, flags, &pidfile);

		if (retval < 0)