linux-stable.git/drivers/tty/tty_io.c, branch linux-3.19.y

tty: fix up atime/mtime mess, take four

2015-03-18T13:11:04+00:00

commit f0bf0bd07943bfde8f5ac39a32664810a379c7d3 upstream.

This problem was taken care of three times already in
* b0de59b5733d18b0d1974a060860a8b5c1b36a2e (TTY: do not update
  atime/mtime on read/write),
* 37b7f3c76595e23257f61bd80b223de8658617ee (TTY: fix atime/mtime
  regression), and
* b0b885657b6c8ef63a46bc9299b2a7715d19acde (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 
Reported-by: John Paul Perry 
Acked-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Greg Kroah-Hartman

tty: Prevent hw state corruption in exclusive mode reopen

2015-01-09T21:46:02+00:00

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 
Signed-off-by: Peter Hurley 
Acked-by: Shreyas Bethur 
Signed-off-by: Greg Kroah-Hartman

tty: Deletion of unnecessary checks before two function calls

2014-11-27T03:35:49+00:00

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 
Signed-off-by: Greg Kroah-Hartman

tty: warn on deprecated serial flags

2014-11-06T23:01:03+00:00

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 
Cc: Peter Hurley 
Cc: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

tty: Call methods in modern style

2014-11-06T04:18:30+00:00

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 
Signed-off-by: Greg Kroah-Hartman

tty: Replace open-coded test with tty_hung_up_p()

2014-11-06T04:18:30+00:00

tty_hung_up_p() is equivalent to the open-coded test in tty_open().

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

Merge branch 'tty-linus' into 'tty-testing'

2014-11-06T03:43:23+00:00

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

tty: Flush ldisc buffer atomically with tty flip buffers

2014-11-06T02:50:43+00:00

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 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Change tty lock order to master->slave

2014-11-06T02:50:42+00:00

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 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

tty: Simplify tty_release() state checks

2014-11-06T02:44:43+00:00

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 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman