linux-stable.git/drivers/tty/tty_io.c, branch v3.10

tty: fix up atime/mtime mess, take three

2013-05-01T14:32:21+00:00

We first tried to avoid updating atime/mtime entirely (commit
b0de59b5733d: "TTY: do not update atime/mtime on read/write"), and then
limited it to only update it occasionally (commit 37b7f3c76595: "TTY:
fix atime/mtime regression"), but it turns out that this was both
insufficient and overkill.

It was insufficient because we let people attach to the shared ptmx node
to see activity without even reading atime/mtime, and it was overkill
because the "only once a minute" means that you can't really tell an
idle person from an active one with 'w'.

So this tries to fix the problem properly.  It marks the shared ptmx
node as un-notifiable, and it lowers the "only once a minute" to a few
seconds instead - still long enough that you can't time individual
keystrokes, but short enough that you can tell whether somebody is
active or not.

Reported-by: Simon Kirby 
Acked-by: Jiri Slaby 
Cc: Greg Kroah-Hartman 
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds

Merge tag 'tty-3.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2013-04-29T19:16:17+00:00

Pull tty/serial driver update from Greg Kroah-Hartman:
 "Here's the big tty/serial driver merge request for 3.10-rc1

  Once again, Jiri has a number of TTY driver fixes and cleanups, and
  Peter Hurley came through with a bunch of ldisc fixes that resolve a
  number of reported issues.  There are some other serial driver
  cleanups as well.

  All of these have been in the linux-next tree for a while"

* tag 'tty-3.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (117 commits)
  tty/serial/sirf: fix MODULE_DEVICE_TABLE
  serial: mxs: drop superfluous {get|put}_device
  serial: mxs: fix buffer overflow
  ARM: PL011: add support for extended FIFO-size of PL011-r1p5
  serial_core.c: add put_device() after device_find_child()
  tty: Fix unsafe bit ops in tty_throttle_safe/unthrottle_safe
  serial: sccnxp: Replace pdata.init/exit with regulator API
  serial: sccnxp: Do not override device name
  TTY: pty, fix compilation warning
  TTY: rocket, fix compilation warning
  TTY: ircomm: fix DTR being raised on hang up
  TTY: synclinkmp: fix DTR being raised on hang up
  TTY: synclink_gt: fix DTR being raised on hang up
  TTY: synclink: fix DTR being raised on hang up
  serial: 8250_dw: Fix the stub for dw8250_probe_acpi()
  serial: 8250_dw: Convert to devm_ioremap()
  serial: 8250_dw: Set port capabilities based on CPR register
  serial: 8250_dw: Let ACPI code extract the DMA client info
  serial: 8250_dw: Support clk framework also with ACPI
  serial: 8250_dw: Enable runtime PM
  ...

TTY: fix atime/mtime regression

2013-04-26T14:59:23+00:00

In commit b0de59b5733d ("TTY: do not update atime/mtime on read/write")
we removed timestamps from tty inodes to fix a security issue and waited
if something breaks.  Well, 'w', the utility to find out logged users
and their inactivity time broke.  It shows that users are inactive since
the time they logged in.

To revert to the old behaviour while still preventing attackers to
guess the password length, we update the timestamps in one-minute
intervals by this patch.

Signed-off-by: Jiri Slaby 
Cc: Greg Kroah-Hartman 
Signed-off-by: Linus Torvalds

tty: tty_vhangup_session can be static

2013-03-25T21:07:34+00:00

Reported-by: Fengguang Wu 
Acked-by: Peter Hurley 

Signed-off-by: Greg Kroah-Hartman

tty: Don't protect atomic operation with mutex

2013-03-18T23:46:31+00:00

test_bit() is already atomic; drop mutex lock/unlock.

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

tty: Bracket ldisc release with TTY_DEBUG_HANGUP messages

2013-03-18T23:46:30+00:00

Expected typical log output:
[    2.437211] tty_open: opening pts1...
[    2.443376] tty_open: opening pts5...
[    2.447830] tty_release: ptm0 (tty count=1)...
[    2.447849] pts0 vhangup...
[    2.447865] tty_release: ptm0: final close
[    2.447876] tty_release: ptm0: freeing structure...
[    2.451634] tty_release: tty1 (tty count=1)...
[    2.451638] tty_release: tty1: final close
[    2.451654] tty_release: tty1: freeing structure...
[    2.452505] tty_release: pts5 (tty count=2)...
[    2.453029] tty_open: opening pts0...

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

tty: Make core responsible for synchronizing its work

2013-03-18T23:44:02+00:00

The tty core relies on the ldisc layer for synchronizing destruction
of the tty. Instead, the final tty release must wait for any pending tty
work to complete prior to tty destruction.

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

tty: Complete ownership transfer of flip buffers

2013-03-18T23:44:02+00:00

Waiting for buffer work to complete is not required for safely
performing changes to the line discipline, once the line discipline
is halted. The buffer work routine, flush_to_ldisc(), will be
unable to acquire an ldisc ref and all existing references were
waited until released (so it can't already have one).

Ensure running buffer work which may reference the soon-to-be-gone
tty completes and any buffer work running after this point retrieves
a NULL tty.

Also, ensure all buffer work is cancelled on port destruction.

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

tty: Don't reenable already enabled ldisc

2013-03-18T23:44:02+00:00

tty_ldisc_hangup() guarantees the ldisc is enabled (or that there
is no ldisc). Since __tty_hangup() was the only user, re-define
tty_ldisc_enable() in file-scope.

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

tty: Signal SIGHUP before hanging up ldisc

2013-03-15T21:02:33+00:00

An exiting session leader can hang if a foreground process is
blocking for line discipline i/o, eg. in n_tty_read(). This happens
because the blocking reader is holding an ldisc reference (indicating
the line discipline is in-use) which prevents __tty_hangup() from
recycling the line discipline. Although waiters are woken before
attempting to gain exclusive access for changing the ldisc, the
blocking reader in this case will not exit the i/o loop since it
has not yet received SIGHUP (because it has not been sent).

Instead, perform signalling first, then recycle the line discipline.

Fixes:

INFO: task init:1 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
init            D 00000000001d7180  2688     1      0 0x00000002
 ffff8800b9acfba8 0000000000000002 00000000001d7180 ffff8800b9b10048
 ffff8800b94cb000 ffff8800b9b10000 00000000001d7180 00000000001d7180
 ffff8800b9b10000 ffff8800b9acffd8 00000000001d7180 00000000001d7180
Call Trace:
 [] __schedule+0x2e9/0x3b0
 [] schedule+0x55/0x60
 [] schedule_timeout+0x3a/0x370
 [] ? mark_held_locks+0xf9/0x130
 [] ? down_failed+0x108/0x200
 [] ? _raw_spin_unlock_irq+0x2b/0x80
 [] ? trace_hardirqs_on_caller+0x128/0x160
 [] down_failed+0x131/0x200
 [] ? tty_ldisc_lock_pair_timeout+0xcd/0x120
 [] ldsem_down_write+0xd3/0x113
 [] ? tty_ldisc_lock_pair_timeout+0xcd/0x120
 [] ? trace_hardirqs_on+0xd/0x10
 [] tty_ldisc_lock_pair_timeout+0xcd/0x120
 [] tty_ldisc_hangup+0xd0/0x220
 [] __tty_hangup+0x137/0x4f0
 [] disassociate_ctty+0x6c/0x230
 [] do_exit+0x41c/0x590
 [] ? syscall_trace_enter+0x24/0x2e0
 [] do_group_exit+0x8a/0xc0
 [] sys_exit_group+0x12/0x20
 [] tracesys+0xe1/0xe6
1 lock held by init/1:
 #0: (&tty->ldisc_sem){++++++}, at: [] tty_ldisc_lock_pair_timeout+0xcd/0x120

Reported-by: Sasha Levin 
Signed-off-by: Peter Hurley 
Acked-by: Jiri Slaby 
Signed-off-by: Greg Kroah-Hartman