Commit 3e7cd6c4 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Linus Torvalds
Browse files

[PATCH] pid: replace is_orphaned_pgrp with is_current_pgrp_orphaned 



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: default avatarEric W. Biederman <ebiederm@xmission.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0475ac08

drivers/char/n_tty.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

drivers/char/tty_io.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

include/linux/tty.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

kernel/exit.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

kernel/signal.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

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