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path: root/drivers/tty/tty_io.c
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Diffstat (limited to 'drivers/tty/tty_io.c')
-rw-r--r--drivers/tty/tty_io.c40
1 files changed, 34 insertions, 6 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 02785d844354..2eefaa6e3e3a 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2128,8 +2128,24 @@ retry_open:
if (!noctty &&
current->signal->leader &&
!current->signal->tty &&
- tty->session == NULL)
- __proc_set_tty(tty);
+ tty->session == NULL) {
+ /*
+ * Don't let a process that only has write access to the tty
+ * obtain the privileges associated with having a tty as
+ * controlling terminal (being able to reopen it with full
+ * access through /dev/tty, being able to perform pushback).
+ * Many distributions set the group of all ttys to "tty" and
+ * grant write-only access to all terminals for setgid tty
+ * binaries, which should not imply full privileges on all ttys.
+ *
+ * This could theoretically break old code that performs open()
+ * on a write-only file descriptor. In that case, it might be
+ * necessary to also permit this if
+ * inode_permission(inode, MAY_READ) == 0.
+ */
+ if (filp->f_mode & FMODE_READ)
+ __proc_set_tty(tty);
+ }
spin_unlock_irq(&current->sighand->siglock);
read_unlock(&tasklist_lock);
tty_unlock(tty);
@@ -2418,7 +2434,7 @@ static int fionbio(struct file *file, int __user *p)
* Takes ->siglock() when updating signal->tty
*/
-static int tiocsctty(struct tty_struct *tty, int arg)
+static int tiocsctty(struct tty_struct *tty, struct file *file, int arg)
{
int ret = 0;
@@ -2452,6 +2468,13 @@ static int tiocsctty(struct tty_struct *tty, int arg)
goto unlock;
}
}
+
+ /* See the comment in tty_open(). */
+ if ((file->f_mode & FMODE_READ) == 0 && !capable(CAP_SYS_ADMIN)) {
+ ret = -EPERM;
+ goto unlock;
+ }
+
proc_set_tty(tty);
unlock:
read_unlock(&tasklist_lock);
@@ -2844,7 +2867,7 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
no_tty();
return 0;
case TIOCSCTTY:
- return tiocsctty(tty, arg);
+ return tiocsctty(tty, file, arg);
case TIOCGPGRP:
return tiocgpgrp(tty, real_tty, p);
case TIOCSPGRP:
@@ -3151,13 +3174,18 @@ struct class *tty_class;
static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
unsigned int index, unsigned int count)
{
+ int err;
+
/* init here, since reused cdevs cause crashes */
driver->cdevs[index] = cdev_alloc();
if (!driver->cdevs[index])
return -ENOMEM;
- cdev_init(driver->cdevs[index], &tty_fops);
+ driver->cdevs[index]->ops = &tty_fops;
driver->cdevs[index]->owner = driver->owner;
- return cdev_add(driver->cdevs[index], dev, count);
+ err = cdev_add(driver->cdevs[index], dev, count);
+ if (err)
+ kobject_put(&driver->cdevs[index]->kobj);
+ return err;
}
/**