From 19e335596658bf1ced262f769a0ed2d72f847766 Mon Sep 17 00:00:00 2001 From: Mark Johnston Date: Thu, 25 Apr 2024 09:35:38 -0400 Subject: [PATCH] kthread: Set *tdptr earlier in kproc_kthread_add() See commit ae77041e0714 ("kthread: Set *newtdp earlier in kthread_add1()") for details. That commit was incomplete since g_init()'s first call to kproc_kthread_add() will cause kproc_kthread_add() to take the `*procptr == NULL` branch, which avoids kthread_create(). To ensure that the thread pointer is initialized before the thread starts running, we have to start the kernel process with RFSTOPPED. We could perhaps go further and use RFSTOPPED only when tdptr != NULL, but it's probably better to have consistent behaviour. Reviewed by: olce, kib Reported by: syzbot+e91e798f3c088215ace6@syzkaller.appspotmail.com MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D44927 (cherry picked from commit d66399326cb4f89d1565fb62c1c07974886893c5) --- sys/kern/kern_kthread.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/sys/kern/kern_kthread.c b/sys/kern/kern_kthread.c index 9cbc7465843..00a264d57a2 100644 --- a/sys/kern/kern_kthread.c +++ b/sys/kern/kern_kthread.c @@ -496,13 +496,21 @@ kproc_kthread_add(void (*func)(void *), void *arg, struct thread *td; if (*procptr == NULL) { + /* + * Use RFSTOPPED to ensure that *tdptr is initialized before the + * thread starts running. + */ error = kproc_create(func, arg, - procptr, flags, pages, "%s", procname); + procptr, flags | RFSTOPPED, pages, "%s", procname); if (error) return (error); td = FIRST_THREAD_IN_PROC(*procptr); if (tdptr) *tdptr = td; + if ((flags & RFSTOPPED) == 0) { + thread_lock(td); + sched_add(td, SRQ_BORING); + } va_start(ap, fmt); vsnprintf(td->td_name, sizeof(td->td_name), fmt, ap); va_end(ap);