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[PATCH] pid: replace is_orphaned_pgrp with is_current_pgrp_orphaned

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Every call to is_orphaned_pgrp passed in process_group(current) which is racy
with respect to another thread changing our process group.  It didn't bite us
because we were dealing with integers and the worse we would get would be a
stale answer.

In switching the checks to use struct pid to be a little more efficient and
prepare the way for pid namespaces this race became apparent.

So I simplified the calls to the more specialized is_current_pgrp_orphaned so
I didn't have to worry about making logic changes to avoid the race.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric W. Biederman 2007-02-12 00:52:58 -08:00 • committed by Linus Torvalds
parent 0475ac0845
commit 3e7cd6c413
5 changed files with 6 additions and 6 deletions
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2
drivers/char/n_tty.c
View file

@ -1188,7 +1188,7 @@ static int job_control(struct tty_struct *tty, struct file *file)
printk("read_chan: tty->pgrp <= 0!\n");
else if (process_group(current) != tty->pgrp) {
if (is_ignored(SIGTTIN) ||
is_orphaned_pgrp(process_group(current)))
is_current_pgrp_orphaned())
return -EIO;
kill_pg(process_group(current), SIGTTIN, 1);
return -ERESTARTSYS;

2
drivers/char/tty_io.c
View file

@ -1118,7 +1118,7 @@ int tty_check_change(struct tty_struct * tty)
return 0;
if (is_ignored(SIGTTOU))
return 0;
if (is_orphaned_pgrp(process_group(current)))
if (is_current_pgrp_orphaned())
return -EIO;
(void) kill_pg(process_group(current), SIGTTOU, 1);
return -ERESTARTSYS;

2
include/linux/tty.h
View file

@ -303,7 +303,7 @@ extern int tty_read_raw_data(struct tty_struct *tty, unsigned char *bufp,
int buflen);
extern void tty_write_message(struct tty_struct *tty, char *msg);
extern int is_orphaned_pgrp(int pgrp);
extern int is_current_pgrp_orphaned(void);
extern int is_ignored(int sig);
extern int tty_signal(int sig, struct tty_struct *tty);
extern void tty_hangup(struct tty_struct * tty);

4
kernel/exit.c
View file

@ -229,12 +229,12 @@ static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignor
return ret; /* (sighing) "Often!" */
}
int is_orphaned_pgrp(int pgrp)
int is_current_pgrp_orphaned(void)
{
int retval;
read_lock(&tasklist_lock);
retval = will_become_orphaned_pgrp(find_pid(pgrp), NULL);
retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
read_unlock(&tasklist_lock);
return retval;

2
kernel/signal.c
View file

@ -1909,7 +1909,7 @@ relock:
/* signals can be posted during this window */
if (is_orphaned_pgrp(process_group(current)))
if (is_current_pgrp_orphaned())
goto relock;
spin_lock_irq(&current->sighand->siglock);