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Date:      Tue, 04 Jul 2023 18:37:37 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 272367] openat(..., O_NONBLOCK | O_EXLOCK) may wrongly return EAGAIN
Message-ID:  <bug-272367-227-q2voB27J2a@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-272367-227@https.bugs.freebsd.org/bugzilla/>
References:  <bug-272367-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D272367

Mateusz Guzik <mjg@FreeBSD.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mjg@FreeBSD.org

--- Comment #1 from Mateusz Guzik <mjg@FreeBSD.org> ---
Quick look suggests this is about the P_ADVLOCK flag, which to my reading is
not being set for the child. Then fdclosexec -> ... -> closef fails to take
action here:

        if (fp->f_type =3D=3D DTYPE_VNODE) {
                vp =3D fp->f_vnode;
                if ((td->td_proc->p_leader->p_flag & P_ADVLOCK) !=3D 0) {
                        lf.l_whence =3D SEEK_SET;
                        lf.l_start =3D 0;
                        lf.l_len =3D 0;
                        lf.l_type =3D F_UNLCK;
                        (void) VOP_ADVLOCK(vp, (caddr_t)td->td_proc->p_lead=
er,
                            F_UNLCK, &lf, F_POSIX);
                }

I don't know what the real semantics are supposed to be here. If any close =
by
*anyone* is supposed to do the unlock, then this should be patched to somet=
hing
like this:

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 908c3352514b..fc03137f6c24 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -2790,7 +2790,7 @@ closef(struct file *fp, struct thread *td)
         */
        if (fp->f_type =3D=3D DTYPE_VNODE) {
                vp =3D fp->f_vnode;
-               if ((td->td_proc->p_leader->p_flag & P_ADVLOCK) !=3D 0) {
+               if ((fp->f_flag & FHASLOCK) !=3D 0) {
                        lf.l_whence =3D SEEK_SET;
                        lf.l_start =3D 0;
                        lf.l_len =3D 0;

--=20
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