Date: Fri, 15 May 2020 12:47:39 +0000 (UTC) From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r361075 - head/sys/kern Message-ID: <202005151247.04FCldp6079421@repo.freebsd.org>
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Author: hselasky Date: Fri May 15 12:47:39 2020 New Revision: 361075 URL: https://svnweb.freebsd.org/changeset/base/361075 Log: Assign process group of the TTY under the "proctree_lock". This fixes a race where concurrent calls to doenterpgrp() and leavepgrp() while TIOCSCTTY is executing may result in tp->t_pgrp changing value so that tty_rel_pgrp() misses clearing it to NULL. For more details refer to the use of pgdelete() in the kernel. No functional change intended. Panic backtrace: __mtx_lock_sleep() # page fault due to using destroyed mutex tty_signal_pgrp() tty_ioctl() ptsdev_ioctl() kern_ioctl() sys_ioctl() amd64_syscall() MFC after: 1 week Sponsored by: Mellanox Technologies Modified: head/sys/kern/tty.c Modified: head/sys/kern/tty.c ============================================================================== --- head/sys/kern/tty.c Fri May 15 12:04:39 2020 (r361074) +++ head/sys/kern/tty.c Fri May 15 12:47:39 2020 (r361075) @@ -1818,7 +1818,6 @@ tty_generic_ioctl(struct tty *tp, u_long cmd, void *da tp->t_session = p->p_session; tp->t_session->s_ttyp = tp; tp->t_sessioncnt++; - sx_xunlock(&proctree_lock); /* Assign foreground process group. */ tp->t_pgrp = p->p_pgrp; @@ -1826,6 +1825,7 @@ tty_generic_ioctl(struct tty *tp, u_long cmd, void *da p->p_flag |= P_CONTROLT; PROC_UNLOCK(p); + sx_xunlock(&proctree_lock); return (0); } case TIOCSPGRP: {
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