Commit 9a5d3023 authored by Oren Laadan's avatar Oren Laadan Committed by Linus Torvalds
Browse files

[PATCH] fork: fix race in setting child's pgrp and tty

In fork, child should recopy parent's pgrp/tty after it has tasklist_lock.
Otherwise following a setpgid() on the parent, *after* copy_signal(), the
child will own a stale pgrp (which may be reused); (eg.  if copy_mm()
sleeps a long while due to memory pressure).  Similar issue for the tty.

Signed-off-by: default avatarOren Laadan <>
Cc: Oleg Nesterov <>
Cc: Roland McGrath <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent fb86a35b
......@@ -811,9 +811,6 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
sig->it_prof_expires = cputime_zero;
sig->it_prof_incr = cputime_zero;
sig->tty = current->signal->tty;
sig->pgrp = process_group(current);
sig->session = current->signal->session;
sig->leader = 0; /* session leadership doesn't inherit */
sig->tty_old_pgrp = 0;
......@@ -1136,15 +1133,15 @@ static task_t *copy_process(unsigned long clone_flags,
attach_pid(p, PIDTYPE_PID, p->pid);
attach_pid(p, PIDTYPE_TGID, p->tgid);
if (thread_group_leader(p)) {
p->signal->tty = current->signal->tty;
p->signal->pgrp = process_group(current);
p->signal->session = current->signal->session;
attach_pid(p, PIDTYPE_PGID, process_group(p));
attach_pid(p, PIDTYPE_SID, p->signal->session);
if (p->pid)
if (!current->signal->tty && p->signal->tty)
p->signal->tty = NULL;
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