Date: Tue, 21 Apr 2026 15:43:56 +0000 Message-ID: <69e79b3c.3406e.44befbe6@gitrepo.freebsd.org>
index | next in thread | raw e-mail
The branch stable/13 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=5eae7f23fe0e189f2d5160772cf6cd4d107dd30a commit 5eae7f23fe0e189f2d5160772cf6cd4d107dd30a Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2026-03-23 15:22:48 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2026-04-21 15:43:53 +0000 tty: Avoid leaving dangling pointers in tty_drop_ctty() The TIOCNOTTY handler detaches the calling process from its controlling terminal. It clears the link from the session to the tty, but not the pointers from the tty to the session and process group. This means that sess_release() doesn't call tty_rel_sess(), and that pgdelete() doesn't call tty_rel_pgrp(), so the pointers are left dangling. Fix this by clearing pointers in tty_drop_ctty(). Add a standalone regression test. Approved by: so Security: FreeBSD-SA-26:10.tty Security: CVE-2026-5398 Reported by: Nicholas Carlini <npc@anthropic.com> Reviewed by: kib, kevans Fixes: 1b50b999f9b5 ("tty: implement TIOCNOTTY") Differential Revision: https://reviews.freebsd.org/D56046 --- sys/kern/tty.c | 4 +++ tests/sys/kern/Makefile | 1 + tests/sys/kern/tiocnotty.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 87 insertions(+) diff --git a/sys/kern/tty.c b/sys/kern/tty.c index 42862ffb8a45..22f3645092f8 100644 --- a/sys/kern/tty.c +++ b/sys/kern/tty.c @@ -1262,6 +1262,10 @@ tty_drop_ctty(struct tty *tp, struct proc *p) session->s_ttydp = NULL; SESS_UNLOCK(session); + if (tp->t_session == session) { + tp->t_session = NULL; + tp->t_pgrp = NULL; + } tp->t_sessioncnt--; p->p_flag &= ~P_CONTROLT; PROC_UNLOCK(p); diff --git a/tests/sys/kern/Makefile b/tests/sys/kern/Makefile index d499fd525222..faf08a352514 100644 --- a/tests/sys/kern/Makefile +++ b/tests/sys/kern/Makefile @@ -35,6 +35,7 @@ ATF_TESTS_C+= subr_physmem_test PLAIN_TESTS_C+= subr_unit_test ATF_TESTS_C+= sysctl_kern_proc ATF_TESTS_C+= sys_getrandom +PLAIN_TESTS_C+= tiocnotty ATF_TESTS_C+= tty_pts ATF_TESTS_C+= unix_passfd_test ATF_TESTS_C+= unix_seqpacket_test diff --git a/tests/sys/kern/tiocnotty.c b/tests/sys/kern/tiocnotty.c new file mode 100644 index 000000000000..2581f976b2ef --- /dev/null +++ b/tests/sys/kern/tiocnotty.c @@ -0,0 +1,82 @@ +/* + * Copyright (c) 2026 Mark Johnston <markj@FreeBSD.org> + * + * SPDX-License-Identifier: BSD-2-Clause + */ + +/* + * A regression test that exercises a bug where TIOCNOTTY would leave some + * dangling pointers behind in the controlling terminal structure. + */ + +#include <sys/ioctl.h> +#include <sys/wait.h> + +#include <err.h> +#include <fcntl.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +int +main(void) +{ + int master, slave, status; + pid_t child; + + master = posix_openpt(O_RDWR | O_NOCTTY); + if (master < 0) + err(1, "posix_openpt"); + if (grantpt(master) < 0) + err(1, "grantpt"); + if (unlockpt(master) < 0) + err(1, "unlockpt"); + + child = fork(); + if (child < 0) + err(1, "fork"); + if (child == 0) { + if (setsid() < 0) + err(1, "setsid"); + slave = open(ptsname(master), O_RDWR | O_NOCTTY); + if (slave < 0) + err(2, "open"); + if (ioctl(slave, TIOCSCTTY, 0) < 0) + err(3, "ioctl(TIOCSCTTY)"); + /* Detach ourselves from the controlling terminal. */ + if (ioctl(slave, TIOCNOTTY, 0) < 0) + err(4, "ioctl(TIOCNOTTY)"); + _exit(0); + } + + if (waitpid(child, &status, 0) < 0) + err(1, "waitpid"); + if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) + errx(1, "child exited with status %d", WEXITSTATUS(status)); + + child = fork(); + if (child < 0) + err(1, "fork"); + if (child == 0) { + struct winsize winsz; + + if (setsid() < 0) + err(1, "setsid"); + slave = open(ptsname(master), O_RDWR | O_NOCTTY); + if (slave < 0) + err(2, "open"); + /* Dereferences dangling t_pgrp pointer in the terminal. */ + memset(&winsz, 0xff, sizeof(winsz)); + if (ioctl(slave, TIOCSWINSZ, &winsz) < 0) + err(3, "ioctl(TIOCSWINSZ)"); + /* Dereferences dangling t_session pointer in the terminal. */ + if (ioctl(slave, TIOCSCTTY, 0) < 0) + err(4, "ioctl(TIOCSCTTY)"); + _exit(0); + } + + if (waitpid(child, &status, 0) < 0) + err(1, "waitpid"); + if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) + errx(1, "child exited with status %d", WEXITSTATUS(status)); +}home | help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?69e79b3c.3406e.44befbe6>