untrusted comment: verify with openbsd-79-base.pub
RWTSdNN9A3yvWLFAZwWGMNkDoOfI5ua8POEssfw5uvdreMlqcLMD6TRSfrgX2tpBtacsl8JyOfP0pYDx1aEedIXf5MhIqncq8wo=

OpenBSD 7.9 errata 013, August 22, 2026:

TIOCGSID on tty(4) could trigger a kernel panic.

Apply by doing:
    signify -Vep /etc/signify/openbsd-79-base.pub -x 013_ttyioctl.patch.sig \
        -m - | (cd /usr/src && patch -p0)

And then rebuild and install a new kernel:
    KK=`sysctl -n kern.osversion | cut -d# -f1`
    cd /usr/src/sys/arch/`machine`/compile/$KK
    make obj
    make config
    make
    make install

Index: sys/kern/tty.c
===================================================================
RCS file: /cvs/src/sys/kern/tty.c,v
diff -u -p -r1.183 tty.c
--- sys/kern/tty.c	16 Apr 2026 14:51:36 -0000	1.183
+++ sys/kern/tty.c	17 Aug 2026 16:50:36 -0000
@@ -845,6 +845,8 @@ ttioctl(struct tty *tp, u_long cmd, cadd
 	case TIOCGSID:			/* get sid of tty */
 		if (!isctty(pr, tp))
 			return (ENOTTY);
+		if (tp->t_session->s_leader == NULL)	/* XXX session stored wrong */
+			return (ENOTTY);
 		*(int *)data = tp->t_session->s_leader->ps_pid;
 		break;
 	case TIOCNXCL:			/* reset exclusive use of tty */