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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: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Konstantin Khlebnikov 2012-01-05 13:04:21 +04:00 committed by Greg Kroah-Hartman
parent dcd6c92267
commit 593a27c4b2
3 changed files with 6 additions and 17 deletions
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8
drivers/tty/pty.c
View File

@ -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)) {

12
drivers/tty/tty_io.c
View File

@ -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)

3
include/linux/tty.h
View File

@ -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);