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Do not use potentially stale thread in kthread_add()

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When an existing process is provided, the thread selected to use
to initialize the new thread could have exited and be reaped.
Acquire the proc lock earlier to ensure the thread remains valid.

Reviewed by:	jhb, julian (previous version)
MFC after:	3 days
This commit is contained in:
Bryan Venteicher 2013-08-17 17:02:43 +00:00
parent f844a115ec
commit e5bbc81be8
1 changed files with 4 additions and 6 deletions
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10
sys/kern/kern_kthread.c
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@ -257,18 +257,17 @@ kthread_add(void (*func)(void *), void *arg, struct proc *p,
panic("kthread_add called too soon");
/* If no process supplied, put it on proc0 */
if (p == NULL) {
if (p == NULL)
p = &proc0;
oldtd = &thread0;
} else {
oldtd = FIRST_THREAD_IN_PROC(p);
}
/* Initialize our new td */
newtd = thread_alloc(pages);
if (newtd == NULL)
return (ENOMEM);
PROC_LOCK(p);
oldtd = FIRST_THREAD_IN_PROC(p);
bzero(&newtd->td_startzero,
__rangeof(struct thread, td_startzero, td_endzero));
bcopy(&oldtd->td_startcopy, &newtd->td_startcopy,
@ -292,7 +291,6 @@ kthread_add(void (*func)(void *), void *arg, struct proc *p,
newtd->td_ucred = crhold(p->p_ucred);
/* this code almost the same as create_thread() in kern_thr.c */
PROC_LOCK(p);
p->p_flag |= P_HADTHREADS;
thread_link(newtd, p);
thread_lock(oldtd);