linux-toradex.git/drivers/tty/pty.c, branch v3.4.73

tty: fix up atime/mtime mess, take three

2013-05-08T02:51:53+00:00

commit b0b885657b6c8ef63a46bc9299b2a7715d19acde upstream.

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 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

TTY: do not reset master's packet mode

2013-03-20T20:04:59+00:00

commit b81273a132177edd806476b953f6afeb17b786d5 upstream.

Now that login from util-linux is forced to drop all references to a
TTY which it wants to hangup (to reach reference count 1) we are
seeing issues with telnet. When login closes its last reference to the
slave PTY, it also resets packet mode on the *master* side. And we
have a race here.

What telnet does is fork+exec of `login'. Then there are two
scenarios:
* `login' closes the slave TTY and resets thus master's packet mode,
  but even now telnet properly sets the mode, or
* `telnetd' sets packet mode on the master, `login' closes the slave
  TTY and resets master's packet mode.

The former case is OK. However the latter happens in much more cases,
by the order of magnitude to be precise. So when one tries to login to
such a messed telnet setup, they see the following:
inux login:
            ogin incorrect

Note the missing first letters -- telnet thinks it is still in the
packet mode, so when it receives "linux login" from `login', it
considers "l" as the type of the packet and strips it.

SuS does not mention how the implementation should behave. Both BSDs I
checked (Free and Net) do not reset the flag upon the last close.

By this I am resurrecting an old bug, see References. We are hitting
it regularly now, i.e. with updated util-linux, ergo login.

Here, I am changing a behavior introduced back in 2.1 times. It would
better have a long time testing before goes upstream.

Signed-off-by: Jiri Slaby 
Cc: Mauro Carvalho Chehab 
Cc: Bryan Mason 
References: https://lkml.org/lkml/2009/11/11/223
References: https://bugzilla.redhat.com/show_bug.cgi?id=504703
References: https://bugzilla.novell.com/show_bug.cgi?id=797042
Signed-off-by: Greg Kroah-Hartman

Remove all #inclusions of asm/system.h

2012-03-28T17:30:03+00:00

Remove all #inclusions of asm/system.h preparatory to splitting and killing
it.  Performed with the following command:

perl -p -i -e 's!^#\s*include\s*.*\n!!' `grep -Irl '^#\s*include\s*' *`

Signed-off-by: David Howells

TTY: remove re-assignments to tty_driver members

2012-03-08T19:37:58+00:00

All num, magic and owner are set by alloc_tty_driver. No need to
re-set them on each allocation site.

pti driver sets something different to what it passes to
alloc_tty_driver. It is not a bug, since we don't use the lines
parameter in any way. Anyway this is fixed, and now we do the right
thing.

Signed-off-by: Jiri Slaby 
Acked-by: Tilman Schmidt 
Signed-off-by: Greg Kroah-Hartman

Revert "TTY: pty, remove superfluous ptm test"

2012-02-24T21:56:36+00:00

This reverts commit a50f724a432997321cabb6c9e665c28e34850f78.

Sasha reported that this causes problems, so revert it.

Cc: Alan Cox 
Cc: Jiri Slaby 
Cc: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

Revert "TTY: get rid of BTM around devpts_*"

2012-02-24T21:55:54+00:00

This reverts commit d3bda5298aad98c7a27678bdd0dd9d008ab9e685.

Sasha reported that this causes problems, so revert it.

Cc: Sasha Levin 
Cc: Jiri Slaby 
Signed-off-by: Greg Kroah-Hartman

TTY: get rid of BTM around devpts_*

2012-02-02T23:10:46+00:00

devpts operations are protected by inode mutexes and dentry
refcounting. There is no need to hold BTM.

Signed-off-by: Jiri Slaby 
Signed-off-by: Greg Kroah-Hartman

TTY: pty, remove superfluous ptm test

2012-02-02T23:10:46+00:00

The code looks like:
if (tty->driver->subtype == PTY_TYPE_MASTER) {
  ...
  if (tty->driver == ptm_driver)

But the second if is superfluous because only the ptm_driver is of
PTY_TYPE_MASTER subtype.

Also we can remove the #if now because devpts_pty_kill is defined as
an empty function for non-CONFIG_UNIX98_PTYS configs.

Signed-off-by: Jiri Slaby 
Acked-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

tty: move pty count limiting into devpts

2012-01-24T22:00:41+00:00

Let's move this stuff to the better place, where we can account pty right in
tty-indexes managing code.

Signed-off-by: Konstantin Khlebnikov 
Signed-off-by: Greg Kroah-Hartman

tty: cleanup prohibition of direct opening for unix98 pty master

2012-01-24T21:56:10+00:00

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 
: Signed-off-by: Linus Torvalds 

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 
Signed-off-by: Greg Kroah-Hartman