diff options
Diffstat (limited to 'drivers/tty/pty.c')
| -rw-r--r-- | drivers/tty/pty.c | 71 |
1 files changed, 67 insertions, 4 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index 2a6bd9ae3f8b..d1399aac05a1 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -24,6 +24,9 @@ #include <linux/slab.h> #include <linux/mutex.h> #include <linux/poll.h> +#include <linux/mount.h> +#include <linux/file.h> +#include <linux/ioctl.h> #undef TTY_DEBUG_HANGUP #ifdef TTY_DEBUG_HANGUP @@ -66,8 +69,13 @@ static void pty_close(struct tty_struct *tty, struct file *filp) #ifdef CONFIG_UNIX98_PTYS if (tty->driver == ptm_driver) { mutex_lock(&devpts_mutex); - if (tty->link->driver_data) - devpts_pty_kill(tty->link->driver_data); + if (tty->link->driver_data) { + struct path *path = tty->link->driver_data; + + devpts_pty_kill(path->dentry); + path_put(path); + kfree(path); + } mutex_unlock(&devpts_mutex); } #endif @@ -440,6 +448,48 @@ err: return retval; } +/** + * pty_open_peer - open the peer of a pty + * @tty: the peer of the pty being opened + * + * Open the cached dentry in tty->link, providing a safe way for userspace + * to get the slave end of a pty (where they have the master fd and cannot + * access or trust the mount namespace /dev/pts was mounted inside). + */ +static struct file *pty_open_peer(struct tty_struct *tty, int flags) +{ + if (tty->driver->subtype != PTY_TYPE_MASTER) + return ERR_PTR(-EIO); + return dentry_open(tty->link->driver_data, flags, current_cred()); +} + +static int pty_get_peer(struct tty_struct *tty, int flags) +{ + int fd = -1; + struct file *filp = NULL; + int retval = -EINVAL; + + fd = get_unused_fd_flags(0); + if (fd < 0) { + retval = fd; + goto err; + } + + filp = pty_open_peer(tty, flags); + if (IS_ERR(filp)) { + retval = PTR_ERR(filp); + goto err_put; + } + + fd_install(fd, filp); + return fd; + +err_put: + put_unused_fd(fd); +err: + return retval; +} + static void pty_cleanup(struct tty_struct *tty) { tty_port_put(tty->port); @@ -613,6 +663,8 @@ static int pty_unix98_ioctl(struct tty_struct *tty, return pty_get_pktmode(tty, (int __user *)arg); case TIOCGPTN: /* Get PT Number */ return put_user(tty->index, (unsigned int __user *)arg); + case TIOCGPTPEER: /* Open the other end */ + return pty_get_peer(tty, (int) arg); case TIOCSIG: /* Send signal to other side of pty */ return pty_signal(tty, (int) arg); } @@ -740,6 +792,7 @@ static int ptmx_open(struct inode *inode, struct file *filp) { struct pts_fs_info *fsi; struct tty_struct *tty; + struct path *pts_path; struct dentry *dentry; int retval; int index; @@ -793,16 +846,26 @@ static int ptmx_open(struct inode *inode, struct file *filp) retval = PTR_ERR(dentry); goto err_release; } - tty->link->driver_data = dentry; + /* We need to cache a fake path for TIOCGPTPEER. */ + pts_path = kmalloc(sizeof(struct path), GFP_KERNEL); + if (!pts_path) + goto err_release; + pts_path->mnt = filp->f_path.mnt; + pts_path->dentry = dentry; + path_get(pts_path); + tty->link->driver_data = pts_path; retval = ptm_driver->ops->open(tty, filp); if (retval) - goto err_release; + goto err_path_put; tty_debug_hangup(tty, "opening (count=%d)\n", tty->count); tty_unlock(tty); return 0; +err_path_put: + path_put(pts_path); + kfree(pts_path); err_release: tty_unlock(tty); // This will also put-ref the fsi |