6.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Brauner <brauner@xxxxxxxxxx> commit 232590ea7fc125986a526e03081b98e5783f70d2 upstream. This reverts commit 3b5bbe798b2451820e74243b738268f51901e7d0. 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: Eric Biggers <ebiggers@xxxxxxxxxx> Link: https://lore.kernel.org/r/20240818035818.GA1929@sol.localdomain Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/fork.c | 25 +++---------------------- 1 file changed, 3 insertions(+), 22 deletions(-) --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2069,23 +2069,10 @@ static int __pidfd_prepare(struct pid *p */ 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) - return -EINVAL; - - /* Don't create pidfds for kernel threads for now. */ - if (tsk->flags & PF_KTHREAD) - return -EINVAL; - } + if (!pid || !pid_has_task(pid, thread ? PIDTYPE_PID : PIDTYPE_TGID)) + return -EINVAL; return __pidfd_prepare(pid, flags, ret); } @@ -2432,12 +2419,6 @@ __latent_entropy struct task_struct *cop 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)
