n_tty: Fix n_tty_write crash when echoing in raw mode

The tty atomic_write_lock does not provide an exclusion guarantee for
the tty driver if the termios settings are LECHO & !OPOST. And since
it is unexpected and not allowed to call TTY buffer helpers like
tty_insert_flip_string concurrently, this may lead to crashes when
concurrect writers call pty_write. In that case the following two
writers:
* the ECHOing from a workqueue and
* pty_write from the process
race and can overflow the corresponding TTY buffer like follows.

If we look into tty_insert_flip_string_fixed_flag, there is:
  int space = __tty_buffer_request_room(port, goal, flags);
  struct tty_buffer *tb = port->buf.tail;
  ...
  memcpy(char_buf_ptr(tb, tb->used), chars, space);
  ...
  tb->used += space;

so the race of the two can result in something like this:
          A                             B
   __tty_buffer_request_room
                                  __tty_buffer_request_room
   memcpy(buf(tb->used), ...)
   tb->used += space;
                                 memcpy(buf(tb->used), ...) ->BOOM

B's memcpy is past the tty_buffer due to the previous A's tb->used
increment.

Since the N_TTY line discipline input processing can output
concurrently with a tty write, obtain the N_TTY ldisc output_lock to
serialize echo output with normal tty writes. This ensures the tty
buffer helper tty_insert_flip_string is not called concurrently and
everything is fine.

Note that this is nicely reproducible by an ordinary user using
forkpty and some setup around that (raw termios + ECHO). And it is
present in kernels at least after commit
d945cb9cce20ac7143c2de8d88b187f62db99bdc (pty: Rework the pty layer to
use the normal buffering logic) in 2.6.31-rc3.

js: add more info to the commit log
js: switch to bool
js: lock unconditionally
js: lock only the tty->ops->write call

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: I9e235db6ec2bb950f26bd8a23f6145dab5dc0a15
Git-commit: 4291086b1f081b869c6d79e5b7441633dc3ace00
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Avijit Kanti Das <avijitnsec@codeaurora.org>
[rsiddoji@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Ravi Kumar S <rsiddoji@codeaurora.org>
msm_bam_rmnet: Fix potential memory corruption

Usage of legacy string manipulation function sprintf could lead to
memory corruption as the number of bytes to be written to the
destination is not bounded. Replace sprintf with snprintf where the
number of bytes to be written is explicitly specified.

CRs-fixed: 672202
Change-Id: Iab7516ad0e2540eb619fe96e26a3516c7adf86cc
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
ARM: add SCHED_HRTICK config option

As we don't include kernel/Kconfig.hz as this defines HZ values
unsuitable for ARM platforms, add the SCHED_HRTICK to properly configure
the scheduler for hrtimer operation.

Change-Id: I1dd68d4b0481bcf37e4bafd9192b29d0509db80f
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
msm: HTC: m7: reset MDP bandwidth values

Change-Id: Ie59d6731f64fcea886091766ac1d3ada10ef0483
msm: HTC: m7: merge display on commands

Change-Id: Ib41307a5d80b4ad92ae8bbe33ad0611e1122656a