From 9a5d3023e626a0baf86ac6b892c983b3db13f22b Mon Sep 17 00:00:00 2001
From: Oren Laadan <orenl@cs.columbia.edu>
Date: Sun, 8 Jan 2006 01:03:51 -0800
Subject: [PATCH] [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: Oren Laadan <orenl@cs.columbia.edu>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
kernel/fork.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 7992ee759d89..4bc0bd8ef176 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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)
__get_cpu_var(process_counts)++;
}
- if (!current->signal->tty && p->signal->tty)
- p->signal->tty = NULL;
-
nr_threads++;
total_forks++;
write_unlock_irq(&tasklist_lock);
--
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