Commit Graph

191 Commits

Author SHA1 Message Date
Peter Hurley
a99cc5d995 tty: Remove !tty check from free_tty_struct()
free_tty_struct() is never called with NULL tty; the two call sites
would already have faulted on earlier access.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 14:28:20 -08:00
Peter Hurley
c8b710b3e4 tty: Fix ldisc leak in failed tty_init_dev()
release_tty() leaks the ldisc instance when called directly (rather
than when releasing the file descriptor from tty_release()).

Since tty_ldisc_release() clears tty->ldisc, releasing the ldisc
instance at tty teardown if tty->ldisc is non-null is not in danger
of double-releasing the ldisc.

Remove deinitialize_tty_struct() now that free_tty_struct() always
performs the tty_ldisc_deinit().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-27 14:28:20 -08:00
Peter Hurley
5c17c861a3 tty: Fix unsafe ldisc reference via ioctl(TIOCGETD)
ioctl(TIOCGETD) retrieves the line discipline id directly from the
ldisc because the line discipline id (c_line) in termios is untrustworthy;
userspace may have set termios via ioctl(TCSETS*) without actually
changing the line discipline via ioctl(TIOCSETD).

However, directly accessing the current ldisc via tty->ldisc is
unsafe; the ldisc ptr dereferenced may be stale if the line discipline
is changing via ioctl(TIOCSETD) or hangup.

Wait for the line discipline reference (just like read() or write())
to retrieve the "current" line discipline id.

Cc: <stable@vger.kernel.org>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-26 23:17:54 -08:00
Peter Hurley
7f22f6c935 tty: Retry failed reopen if tty teardown in-progress
A small window exists where a tty reopen will observe the tty
just prior to imminent teardown (tty->count == 0); in this case, open()
returns EIO to userspace.

Instead, retry the open after checking for signals and yielding;
this interruptible retry loop allows teardown to commence and initialize
a new tty on retry. Never retry the BSD master pty reopen; there is no
guarantee the pty pair teardown is imminent since the slave file
descriptors may remain open indefinitely.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 4.4
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-26 23:17:54 -08:00
Peter Hurley
0bfd464d3f tty: Wait interruptibly for tty lock on reopen
Allow a signal to interrupt the wait for a tty reopen; eg., if
the tty has starting final close and is waiting for the device to
drain.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 4.4
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-26 23:17:54 -08:00
Peter Hurley
d1d3a0f744 tty: Only allow slave pty as controlling tty
A master pty should never be a controlling tty in Linux; if the
master pty is specified to ioctl(TIOCSCTTY), silently substitute the slave
pty as the controlling tty.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
83db1df446 tty: core: Prefer dev_dbg() over pr_debug()
Where possible, use dev_dbg() instead of pr_debug()

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
d435cefe9c tty: Remove __func__ from tty_debug() macro
Now that tty_debug() macro uses pr_debug(), the function name can
be printed when using dynamic debug; printing the function name within
the format string is redundant.

Remove the __func__ parameter and print specifier from the format string.
Add context to messages for when the function name is not printed by
dynamic debug, or when dynamic debug is not enabled.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
89222e6266 tty: core: Prefer pr_* to printk(*)
Convert remaining printk() use to pr_*() when tty is unknown or
unsafe to use.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
656fb86770 tty: core: Add driver name to invalid device registration message
Include the driver name in the tty_register_device_attr() error
message for invalid index.

Note that tty_err() cannot be used here because there is no tty;
use pr_err().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
9b42bb750f tty: Convert SAK messages to tty_notice()
Use tty_notice() for unified message format from the tty core.
Fix each message to accurately reflect the cause of each termination.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
339f36ba14 tty: Define tty_*() printk macros
Since not all ttys are devices (eg., SysV ptys), dev_*() printk macros
cannot be used. Define tty_*() printk macros that output in similar
format to dev_*() macros (ie., <driver> <tty>: .....).

Transform the most-trivial printk( LEVEL ...) usage to tty_*() usage.
NB: The function name has been eliminated from messages with unique
context, or prefixed to the format when given.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
0a083eddae tty: core: Add helper fn to deref tty driver name
Similar to tty_name(), add tty_driver_name() helper to safely
dereference tty->driver->name (otherwise return empty string).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
25080652a2 tty: core: Remove redundant oom message
kmalloc() already emits a diagnostic for failed allocations; remove
tty-specific message.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
82b8f888e9 tty: Make tty_paranoia_check() file scope
tty_paranoia_check() is only used within drivers/tty/tty_io.c;
remove extern declaration in header and limit symbol to file scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-12-13 19:59:48 -08:00
Peter Hurley
ee0c1a65cf tty: Fix tty_send_xchar() lock order inversion
The correct lock order is atomic_write_lock => termios_rwsem, as
established by tty_write() => n_tty_write().

Fixes: c274f6ef1c ("tty: Hold termios_rwsem for tcflow(TCIxxx)")
Reported-and-Tested-by: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org> # v3.18+
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-11-20 16:19:54 -08:00
Peter Hurley
e176058f0d tty: Abstract tty buffer work
Introduce API functions to restart and cancel tty buffer work, rather
than manipulate buffer work directly.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-17 21:32:21 -07:00
Peter Hurley
4b41b9539a tty: Prevent tty teardown during tty_write_message()
tty_write_message() allows the caller to directly write to a specific
tty. Since the line discipline is bypassed for the direct write,
nothing prevents the tty from being torn down after the tty count is
checked.

Hold the tty lock for the duration of the direct write.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-17 21:30:49 -07:00
Peter Hurley
1e86b5bf15 tty: core: Use correct spinlock flavor in tiocspgrp()
tiocspgrp() is the ioctl handler for TIOCSPGRP, which runs in
non-atomic context; use spin_lock/unlock_irq (since interrupt state
is on).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-17 21:30:49 -07:00
Peter Hurley
2812d9e9fd tty: Combine SIGTTOU/SIGTTIN handling
The job_control() check in n_tty_read() has nearly identical purpose
and results as tty_check_change(). Both functions' purpose is to
determine if the current task's pgrp is the foreground pgrp for the tty,
and if not, to signal the current pgrp.

Introduce __tty_check_change() which takes the signal to send
and performs the shared operations for job control() and
tty_check_change().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-17 21:30:49 -07:00
Jann Horn
0c55627167 drivers/tty: require read access for controlling terminal
This is mostly a hardening fix, given that write-only access to other
users' ttys is usually only given through setgid tty executables.

Signed-off-by: Jann Horn <jann@thejh.net>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-04 19:20:30 +01:00
Leon Yu
c1a752ba2d tty: don't leak cdev in tty_cdev_add()
Commit a3a10ce342 ("Avoid usb reset crashes by making tty_io cdevs truly
dynamic") which mixes using cdev_alloc() and cdev_init() is problematic.
Subsequent call to cdev_init() after cdev_alloc() sets kobj release method
from cdev_dynamic_release() to cdev_default_release() and thus makes it
impossible to free allocated cdev.

This patch also consolidates error path of cdev_add() as cdev can also leak
here if things went wrong.

Signed-off-by: Leon Yu <chianglungyu@gmail.com>
Fixes: a3a10ce342 ("Avoid usb reset crashes by making tty_io cdevs truly dynamic")
Acked-by: Richard Watts <rrw@kynesim.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-04 18:51:42 +01:00
Richard Watts
a3a10ce342 Avoid usb reset crashes by making tty_io cdevs truly dynamic
Avoid usb reset crashes by making tty_io cdevs truly dynamic

Signed-off-by: Richard Watts <rrw@kynesim.co.uk>
Reported-by: Duncan Mackintosh <DMackintosh@cbnl.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-08-03 15:24:43 -07:00
Peter Hurley
accff793af tty: Replace #ifdef TTY_DEBUG_HANGUP with tty_debug_hangup()
Add tty_debug_hangup() macro which uses tty_debug to print the
debug message; remove inlined #ifdefs.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-07-23 18:37:31 -07:00
Peter Hurley
e2dfa3d387 tty: core: Add tty_debug() for printk(KERN_DEBUG) messages
Introduce tty_debug() macro to output uniform debug information for
tty core debug messages (function name and tty name).

Note: printk(KERN_DEBUG) is retained here over pr_debug() since
messages can be enabled in non-DEBUG builds.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-07-23 18:37:31 -07:00
Peter Hurley
3a6b02dc1f tty: core: Improve debug message content
Output the function name, tty name, and invariant failure (if applicable).
Add the tty count to the tty_open() message. Fix the disassociate_ctty()
message, which printed the NULL pointer and the wrong message.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-07-23 18:31:29 -07:00
Patrick Donnelly
6719693ca2 tty: add missing rcu_read_lock for task_pgrp
task_pgrp requires an rcu or tasklist lock to be obtained if the returned pid
is to be dereferenced, which kill_pgrp does. Obtain an RCU lock for the
duration of use.

Signed-off-by: Patrick Donnelly <batrick@batbytes.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-07-23 17:56:38 -07:00
Rasmus Villemoes
429b474990 tty: remove buf parameter from tty_name()
tty_name no longer uses the buf parameter, so remove it along with all
the 64 byte stack buffers that used to be passed in.

Mostly generated by the coccinelle script

@depends on patch@
identifier buf;
constant C;
expression tty;
@@
- char buf[C];
  <+...
- tty_name(tty, buf)
+ tty_name(tty)
  ...+>

allmodconfig compiles, so I'm fairly confident the stack buffers
weren't used for other purposes as well.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-05-06 22:26:57 +02:00
Rasmus Villemoes
917162c936 tty: return tty->name directly from tty_name
All users of tty_name pass the return value (the provided buffer) to
some printf-like function. We can thus avoid the strcpy and, more
importantly, later remove the buf parameter completely, eliminating
the need for some 64 byte stack buffers.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-05-06 22:26:57 +02:00
Rasmus Villemoes
1d6b98774c tty: constify return type of tty_name
All users of tty_name pass the result directly to a printf-like
function. This means we can actually let tty_name return the literal
"NULL tty" or tty->name directly, avoiding the strcpy and a lot of
medium-sized stack buffers. In preparation for that, make the return
type const char*.

While at it, we can also constify the tty parameter.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-05-06 22:26:57 +02:00
Greg Kroah-Hartman
fbf4763531 tty: clean up the tty time logic a bit
We only care if anything other than the lower 3 bits of the tty has
changed, so just check that way, which makes it a bit faster, and more
obvious what is going on.  Also, document this for future developers to
understand why we did this.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
2015-03-26 23:10:27 +01:00
Takashi Iwai
1083a7be45 tty: Use static attribute groups for sysfs entries
Instead of manual calls of device_create_file() and
device_remove_file(), pass the static attribute groups using
device_create_with_groups().

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-03-26 16:10:10 +01:00
Jiri Slaby
f0bf0bd079 tty: fix up atime/mtime mess, take four
This problem was taken care of three times already in
* b0de59b573 (TTY: do not update
  atime/mtime on read/write),
* 37b7f3c765 (TTY: fix atime/mtime
  regression), and
* b0b885657b (tty: fix up atime/mtime
  mess, take three)

But it still misses one point. As John Paul correctly points out, we
do not care about setting date. If somebody ever changes wall
time backwards (by mistake for example), tty timestamps are never
updated until the original wall time passes.

So check the absolute difference of times and if it large than "8
seconds or so", always update the time. That means we will update
immediatelly when changing time. Ergo, CAP_SYS_TIME can foul the
check, but it was always that way.

Thanks John for serving me this so nicely debugged.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: John Paul Perry <john_paul.perry@alcatel-lucent.com>
Cc: <stable@vger.kernel.org> # all, as b0b885657 was backported
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-03-07 03:06:51 +01:00
Peter Hurley
86f2c00f1d tty: Prevent hw state corruption in exclusive mode reopen
Exclusive mode ttys (TTY_EXCLUSIVE) do not allow further reopens;
fail the condition before associating the file pointer and calling
the driver open() method.

Prevents DTR programming when the tty is already in exclusive mode.

Reported-by: Shreyas Bethur <shreyas.bethur@ni.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Shreyas Bethur <shreyas.bethur@ni.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-01-09 13:46:02 -08:00
Markus Elfring
a211b1af19 tty: Deletion of unnecessary checks before two function calls
The functions put_device() and tty_kref_put() test whether their argument
is NULL and then return immediately.
Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-26 19:35:49 -08:00
Jiri Slaby
8a8ae62f82 tty: warn on deprecated serial flags
When somebody calls TIOCSSERIAL ioctl with serial flags to set one of
* ASYNC_SESSION_LOCKOUT
* ASYNC_PGRP_LOCKOUT
* ASYNC_CALLOUT_NOHUP
* ASYNC_AUTOPROBE
nothing happens. We actually ignore the flags for over a decade at
least (I checked 2.6.0).

So start yelling at users who use those flags, that they shouldn't.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-06 15:01:03 -08:00
Peter Hurley
c961bfb174 tty: Call methods in modern style
The use of older function ptr calling style, (*fn)(), makes static
analysis more error-prone; replace with modern fn() style.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 20:18:30 -08:00
Peter Hurley
1256937f04 tty: Replace open-coded test with tty_hung_up_p()
tty_hung_up_p() is equivalent to the open-coded test in tty_open().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 20:18:30 -08:00
Greg Kroah-Hartman
28e1445c65 Merge branch 'tty-linus' into 'tty-testing'
We need the fixes in drivers/tty/tty_io.c that were done in there for
future patches in this branch.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 19:43:23 -08:00
Peter Hurley
86c80a8e2a tty: Flush ldisc buffer atomically with tty flip buffers
tty_ldisc_flush() first clears the line discipline input buffer,
then clears the tty flip buffers. However, this allows for existing
data in the tty flip buffers to be added after the ldisc input
buffer has been cleared, but before the flip buffers have been cleared.

Add an optional ldisc parameter to tty_buffer_flush() to allow
tty_ldisc_flush() to pass the ldisc to clear.

NB: Initially, the plan was to do this automatically in
tty_buffer_flush(). However, an audit of the behavior of existing
line disciplines showed that performing a ldisc buffer flush on
ioctl(TCFLSH) was not always the outcome. For example, some line
disciplines have flush_buffer() methods but not ioctl() methods,
so a ->flush_buffer() command would be unexpected.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:50:43 -08:00
Peter Hurley
2aff5e2bc6 tty: Change tty lock order to master->slave
When releasing the master pty, the slave pty also needs to be locked
to prevent concurrent tty count changes for the slave pty and to
ensure that only one parallel master and slave release observe the
final close, and proceed to destruct the pty pair. Conversely, when
releasing the slave pty, locking the master pty is not necessary
(since the master's state can be inferred by the slave tty count).

Introduce tty_lock_slave()/tty_unlock_slave() which acquires/releases
the tty lock of the slave pty. Remove tty_lock_pair()/tty_unlock_pair().

Dropping the tty_lock is no longer required to re-establish a stable
lock order.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:50:42 -08:00
Peter Hurley
7ffb6da93c tty: Simplify tty_release() state checks
The local o_tty variable in tty_release() is now accessed only
when closing the pty master.

Set o_tty to slave pty when closing pty master, otherwise NULL;
use o_tty != NULL as replacement for pty_master.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:44:43 -08:00
Peter Hurley
359b9fb5c4 tty: Simplify tty_release_checks() interface
Passing the 'other' tty to tty_release_checks() only makes sense
for a pty pair; make o_tty scope local instead.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:43:27 -08:00
Peter Hurley
62462aefeb tty: Simplify tty_ldisc_release() interface
Passing the 'other' tty to tty_ldisc_release() only makes sense
for a pty pair; make o_tty function local instead.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:42:46 -08:00
Peter Hurley
949aa64ff9 tty: Fold pty pair handling into tty_flush_works()
Perform work flush for both ends of a pty pair within tty_flush_works(),
rather than calling twice.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:42:46 -08:00
Peter Hurley
324c1650ca tty: Simplify pty pair teardown logic
When the slave side closes and its tty count is 0, the pty
pair can be destroyed; the master side must have already
closed for the slave side tty count to be 0. Thus, only the
pty master close must check if the slave side has closed by
checking the slave tty count.

Remove the pre-computed closing flags and check the actual count(s).
Regular ttys are unaffected by this change.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:42:15 -08:00
Peter Hurley
deb287e740 tty: Document check_tty_count() requires tty_lock held
Holding the tty_lock() is necessary to prevent concurrent changes
to the tty count that may cause it to differ from the open file
list count. The tty_lock() is already held at all call sites.

NB: Note that the check for the pty master tty count is safe because
the slave's tty_lock() is held while decrementing the pty master
tty count.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:41:22 -08:00
Peter Hurley
d5e370a4ee tty: Don't release tty locks for wait queue sanity check
Releasing the tty locks while waiting for the tty wait queues to
be empty is no longer necessary nor desirable. Prior to
"tty: Don't take tty_mutex for tty count changes", dropping the
tty locks was necessary to reestablish the correct lock order between
tty_mutex and the tty locks. Dropping the global tty_mutex was necessary;
otherwise new ttys could not have been opened while waiting.

However, without needing the global tty_mutex held, the tty locks for
the releasing tty can now be held through the sleep. The sanity check
is for abnormal conditions caused by kernel bugs, not for recoverable
errors caused by misbehaving userspace; dropping the tty locks only
allows the tty state to get more sideways.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:39:59 -08:00
Peter Hurley
0911261d4c tty: Don't take tty_mutex for tty count changes
Holding tty_mutex is no longer required to serialize changes to
the tty_count or to prevent concurrent opens of closing ttys;
tty_lock() is sufficient.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:30:43 -08:00
Peter Hurley
04980706c8 tty: Remove TTY_CLOSING
Now that re-open is not permitted for a legacy BSD pty master,
using TTY_CLOSING to indicate when a tty can be torn-down is
no longer necessary.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-05 18:24:10 -08:00