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In tty_makedev() the following construction:

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dev = make_dev_cred();
dev->si_drv1 = tp;

leaves a small window where the newly created device may be opened
and si_drv1 is NULL.

As this is a vary rare situation, using a lock to close the window
seems overkill. Instead just wait for the assignment of si_drv1.

Suggested by:	kib
MFC after:	1 week
This commit is contained in:
Peter Holm 2012-06-18 07:34:38 +00:00
parent 8a3860d5b4
commit e84a11e7ff
1 changed files with 19 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
sys/kern/tty.c
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@ -219,9 +219,15 @@ ttydev_leave(struct tty *tp)
static int
ttydev_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
{
struct tty *tp = dev->si_drv1;
struct tty *tp;
int error = 0;
while ((tp = dev->si_drv1) == NULL) {
error = tsleep(&dev->si_drv1, PCATCH, "ttdrv1", 1);
if (error != EWOULDBLOCK)
return (error);
}
tty_lock(tp);
if (tty_gone(tp)) {
/* Device is already gone. */
@ -738,9 +744,14 @@ static struct cdevsw ttydev_cdevsw = {
static int
ttyil_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
{
struct tty *tp = dev->si_drv1;
struct tty *tp;
int error = 0;
while ((tp = dev->si_drv1) == NULL) {
error = tsleep(&dev->si_drv1, PCATCH, "ttdrv1", 1);
if (error != EWOULDBLOCK)
return (error);
}
tty_lock(tp);
if (tty_gone(tp))
error = ENODEV;
@ -1203,6 +1214,7 @@ tty_makedev(struct tty *tp, struct ucred *cred, const char *fmt, ...)
dev = make_dev_cred(&ttydev_cdevsw, 0, cred,
uid, gid, mode, "%s%s", prefix, name);
dev->si_drv1 = tp;
wakeup(&dev->si_drv1);
tp->t_dev = dev;
/* Slave call-in devices. */
@ -1211,12 +1223,14 @@ tty_makedev(struct tty *tp, struct ucred *cred, const char *fmt, ...)
uid, gid, mode, "%s%s.init", prefix, name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
wakeup(&dev->si_drv1);
dev->si_drv2 = &tp->t_termios_init_in;
dev = make_dev_cred(&ttyil_cdevsw, TTYUNIT_LOCK, cred,
uid, gid, mode, "%s%s.lock", prefix, name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
wakeup(&dev->si_drv1);
dev->si_drv2 = &tp->t_termios_lock_in;
}
@ -1226,6 +1240,7 @@ tty_makedev(struct tty *tp, struct ucred *cred, const char *fmt, ...)
UID_UUCP, GID_DIALER, 0660, "cua%s", name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
wakeup(&dev->si_drv1);
/* Slave call-out devices. */
if (tp->t_flags & TF_INITLOCK) {
@ -1234,6 +1249,7 @@ tty_makedev(struct tty *tp, struct ucred *cred, const char *fmt, ...)
UID_UUCP, GID_DIALER, 0660, "cua%s.init", name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
wakeup(&dev->si_drv1);
dev->si_drv2 = &tp->t_termios_init_out;
dev = make_dev_cred(&ttyil_cdevsw,
@ -1241,6 +1257,7 @@ tty_makedev(struct tty *tp, struct ucred *cred, const char *fmt, ...)
UID_UUCP, GID_DIALER, 0660, "cua%s.lock", name);
dev_depends(tp->t_dev, dev);
dev->si_drv1 = tp;
wakeup(&dev->si_drv1);
dev->si_drv2 = &tp->t_termios_lock_out;
}
}