The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=75be70064483158da2b89ab412f83a4694560e58
commit 75be70064483158da2b89ab412f83a4694560e58 Author: Mark Johnston <[email protected]> AuthorDate: 2026-07-27 23:12:37 +0000 Commit: Mark Johnston <[email protected]> CommitDate: 2026-07-27 23:12:37 +0000 umtx: Do not make an exiting thread the owner of a PI mutex Otherwise an assertion in umtx_thread_alloc() (TAILQ_EMPTY(&uq->uq_pi_contested)) is violated. This use of TDB_EXIT is hacky, but I cannot see another way to check for an exiting thread without adding some more overhead to kern_thr_exit(). Fixes: 2a339d9e3dc1 Reported by: Maik Muench of Secfault Security Reviewed by: kib MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D58447 --- sys/kern/kern_umtx.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c index ab6e578ab380..4f6e2b339ba6 100644 --- a/sys/kern/kern_umtx.c +++ b/sys/kern/kern_umtx.c @@ -2028,7 +2028,7 @@ int umtxq_sleep_pi(struct umtx_q *uq, struct umtx_pi *pi, uint32_t owner, const char *wmesg, struct umtx_abs_timeout *timo, bool shared) { - struct thread *td, *td1; + struct thread *td; struct umtx_q *uq1; int error, pri; #ifdef INVARIANTS @@ -2044,13 +2044,22 @@ umtxq_sleep_pi(struct umtx_q *uq, struct umtx_pi *pi, uint32_t owner, umtxq_insert(uq); mtx_lock(&umtx_lock); if (pi->pi_owner == NULL) { + struct thread *ownertd; + mtx_unlock(&umtx_lock); - td1 = tdfind(owner, shared ? -1 : td->td_proc->p_pid); + ownertd = tdfind(owner, shared ? -1 : td->td_proc->p_pid); mtx_lock(&umtx_lock); - if (td1 != NULL) { - if (pi->pi_owner == NULL) - umtx_pi_setowner(pi, td1); - PROC_UNLOCK(td1->td_proc); + if (ownertd != NULL) { + /* + * An exiting thread that has already called + * umtx_thread_exit() must not be made the owner of a + * shared mutex. + */ + if ((ownertd->td_proc->p_flag & P_WEXIT) == 0 && + (ownertd->td_dbgflags & TDB_EXIT) == 0 && + pi->pi_owner == NULL) + umtx_pi_setowner(pi, ownertd); + PROC_UNLOCK(ownertd->td_proc); } }
