The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 3b5bbe798b2451820e74243b738268f51901e7d0 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024081908-dork-steadfast-6a68@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..
Possible dependencies:
3b5bbe798b24 ("pidfd: prevent creation of pidfds for kthreads") 83b290c9e3b5 ("pidfd: clone: allow CLONE_THREAD | CLONE_PIDFD together") 64bef697d33b ("pidfd: implement PIDFD_THREAD flag for pidfd_open()") 21e25205d7f9 ("pidfd: don't do_notify_pidfd() if !thread_group_empty()") cdefbf2324ce ("pidfd: cleanup the usage of __pidfd_prepare's flags") 932562a6045e ("rseq: Split out rseq.h from sched.h") cba6167f0adb ("restart_block: Trim includes") f038cc1379c0 ("locking/seqlock: Split out seqlock_types.h") 53d31ba842d9 ("posix-cpu-timers: Split out posix-timers_types.h") f995443f01b4 ("locking/seqlock: Simplify SEQCOUNT_LOCKNAME()")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 3b5bbe798b2451820e74243b738268f51901e7d0 Mon Sep 17 00:00:00 2001 From: Christian Brauner brauner@kernel.org Date: Wed, 31 Jul 2024 12:01:12 +0200 Subject: [PATCH] pidfd: prevent creation of pidfds for kthreads
It's currently possible to create pidfds for kthreads but it is unclear what that is supposed to mean. Until we have use-cases for it and we figured out what behavior we want block the creation of pidfds for kthreads.
Link: https://lore.kernel.org/r/20240731-gleis-mehreinnahmen-6bbadd128383@brauner Fixes: 32fcb426ec00 ("pid: add pidfd_open()") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner brauner@kernel.org
diff --git a/kernel/fork.c b/kernel/fork.c index cc760491f201..18bdc87209d0 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2053,11 +2053,24 @@ 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) { - bool thread = flags & PIDFD_THREAD; - - if (!pid || !pid_has_task(pid, thread ? PIDTYPE_PID : PIDTYPE_TGID)) + if (!pid) return -EINVAL;
+ scoped_guard(rcu) { + struct task_struct *tsk; + + 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; + } + return __pidfd_prepare(pid, flags, ret); }
@@ -2403,6 +2416,12 @@ __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)