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kthread: Set *tdptr earlier in kproc_kthread_add()

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See commit ae77041e07 ("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
This commit is contained in:
Mark Johnston 2024-04-25 09:35:38 -04:00
parent 42255af64a
commit d66399326c
1 changed files with 9 additions and 1 deletions
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10
sys/kern/kern_kthread.c
View file

@ -495,13 +495,21 @@ 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);