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Commit 593a27c4 authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Greg Kroah-Hartman
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tty: cleanup prohibition of direct opening for unix98 pty master 



cleanup hack added in v2.6.27-3203-g15582d3

comment from that patch:

: pty: If the administrator creates a device for a ptmx slave we should not error
:
: The open path for ptmx slaves is via the ptmx device. Opening them any
: other way is not allowed. Vegard Nossum found that previously this was not
: the case and mknod foo c 128 42; cat foo would produce nasty diagnostics
:
: Signed-off-by: Alan Cox <alan@redhat.com>
: Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

devpts_get_tty() returns non-null only for inodes on devpts, but there is no
inodes for master-devices, /dev/ptmx (/dev/pts/ptmx) is the only way to open them.
Thus we can completely forbid lookup for master-devices and eliminate that hack in
tty_init_dev() because tty_open() will get EIO from tty_driver_lookup_tty().

Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent dcd6c922

drivers/tty/pty.c

+3 −5
Original line number Diff line number Diff line
@@ -515,10 +515,8 @@ static int pty_unix98_ioctl(struct tty_struct *tty, 
static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,

		struct inode *ptm_inode, int idx)

{

	struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);

	if (tty)

		tty = tty->link;

	return tty;

	/* Master must be open via /dev/ptmx */

	return ERR_PTR(-EIO);

}



/**
@@ -677,7 +675,7 @@ static int ptmx_open(struct inode *inode, struct file *filp) 


	mutex_lock(&tty_mutex);

	tty_lock();

	tty = tty_init_dev(ptm_driver, index, 1);

	tty = tty_init_dev(ptm_driver, index);

	mutex_unlock(&tty_mutex);



	if (IS_ERR(tty)) {

drivers/tty/tty_io.c

+2 −10
Original line number Diff line number Diff line
@@ -1365,7 +1365,6 @@ static int tty_reopen(struct tty_struct *tty) 
 *	@driver: tty driver we are opening a device on

 *	@idx: device index

 *	@ret_tty: returned tty structure

 *	@first_ok: ok to open a new device (used by ptmx)

 *

 *	Prepare a tty device. This may not be a "new" clean device but

 *	could also be an active device. The pty drivers require special
@@ -1385,18 +1384,11 @@ static int tty_reopen(struct tty_struct *tty) 
 * relaxed for the (most common) case of reopening a tty.

 */



struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,

								int first_ok)

struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)

{

	struct tty_struct *tty;

	int retval;



	/* Check if pty master is being opened multiple times */

	if (driver->subtype == PTY_TYPE_MASTER &&

		(driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {

		return ERR_PTR(-EIO);

	}



	/*

	 * First time open is complex, especially for PTY devices.

	 * This code guarantees that either everything succeeds and the
@@ -1950,7 +1942,7 @@ static int tty_open(struct inode *inode, struct file *filp) 
		if (retval)

			tty = ERR_PTR(retval);

	} else

		tty = tty_init_dev(driver, index, 0);

		tty = tty_init_dev(driver, index);



	mutex_unlock(&tty_mutex);

	if (driver)

include/linux/tty.h

+1 −2
Original line number Diff line number Diff line
@@ -480,8 +480,7 @@ extern void free_tty_struct(struct tty_struct *tty); 
extern void initialize_tty_struct(struct tty_struct *tty,

		struct tty_driver *driver, int idx);

extern void deinitialize_tty_struct(struct tty_struct *tty);

extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,

								int first_ok);

extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx);

extern int tty_release(struct inode *inode, struct file *filp);

extern int tty_init_termios(struct tty_struct *tty);