git: 676be27133fa - main - libpthread_init(): ensure curthread == NULL until set explicitly

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=676be27133fa3296f3d9083732d8837a3eaa5ea4

commit 676be27133fa3296f3d9083732d8837a3eaa5ea4
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2025-01-14 22:11:48 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2025-01-14 23:14:00 +0000

    libpthread_init(): ensure curthread == NULL until set explicitly
    
    Otherwise libthr::_get_curthread() returns a garbage kept there from
    allocate_initial_tls(), until libthr initialization proceeds enough to
    set initial pcb->pcb_thread.  The garbage pcb_thread was dereferenced
    as struct pthread and some memory read as TID.  Since the read might not
    be consistent between reads, thr_malloc_umtx unlock sometimes returned
    EPERM instead of clearing the lock word.
    
    Reported by:    markj
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
---
 lib/libthr/thread/thr_init.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/libthr/thread/thr_init.c b/lib/libthr/thread/thr_init.c
index 708c425d69c1..8855491b91cb 100644
--- a/lib/libthr/thread/thr_init.c
+++ b/lib/libthr/thread/thr_init.c
@@ -334,6 +334,8 @@ _libpthread_init(struct pthread *curthread)
 	/* Set the initial thread. */
 	if (curthread == NULL) {
 		first = 1;
+		/* Force _get_curthread() return NULL until set. */
+		_tcb_get()->tcb_thread = NULL;
 		/* Create and initialize the initial thread. */
 		curthread = _thr_alloc(NULL);
 		if (curthread == NULL)