linux.git/drivers/tty, branch v3.15

Staging: speakup: Update __speakup_paste_selection() tty (ab)usage to match vt

2014-05-23T17:25:11+00:00

This function is largely a duplicate of paste_selection() in
drivers/tty/vt/selection.c, but with its own selection state.  The
speakup selection mechanism should really be merged with vt.

For now, apply the changes from 'TTY: vt, fix paste_selection ldisc
handling', 'tty: Make ldisc input flow control concurrency-friendly',
and 'tty: Fix unsafe vt paste_selection()'.

References: https://bugs.debian.org/735202
References: https://bugs.debian.org/744015
Reported-by: Paul Gevers 
Reported-and-tested-by: Jarek Czekalski 
Signed-off-by: Ben Hutchings 
Cc:  # v3.8 but needs backporting for < 3.12
Signed-off-by: Greg Kroah-Hartman

tty: Fix lockless tty buffer race

2014-05-03T22:14:28+00:00

Commit 6a20dbd6caa2358716136144bf524331d70b1e03,
"tty: Fix race condition between __tty_buffer_request_room and flush_to_ldisc"
correctly identifies an unsafe race condition between
__tty_buffer_request_room() and flush_to_ldisc(), where the consumer
flush_to_ldisc() prematurely advances the head before consuming the
last of the data committed. For example:

           CPU 0                     |            CPU 1
__tty_buffer_request_room            | flush_to_ldisc
  ...                                |   ...
                                     |   count = head->commit - head->read
  n = tty_buffer_alloc()             |
  b->commit = b->used                |
  b->next = n                        |
                                     |   if (!count)                /* T */
                                     |     if (head->next == NULL)  /* F */
                                     |     buf->head = head->next

In this case, buf->head has been advanced but head->commit may have
been updated with a new value.

Instead of reintroducing an unnecessary lock, fix the race locklessly.
Read the commit-next pair in the reverse order of writing, which guarantees
the commit value read is the latest value written if the head is
advancing.

Reported-by: Manfred Schlaegl 
Cc:  # 3.12.x+
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

Revert "tty: Fix race condition between __tty_buffer_request_room and flush_to_ldisc"

2014-05-03T22:14:28+00:00

This reverts commit 6a20dbd6caa2358716136144bf524331d70b1e03.

Although the commit correctly identifies an unsafe race condition
between __tty_buffer_request_room() and flush_to_ldisc(), the commit
fixes the race with an unnecessary spinlock in a lockless algorithm.

The follow-on commit, "tty: Fix lockless tty buffer race" fixes
the race locklessly.

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

drivers/tty/hvc: don't free hvc_console_setup after init

2014-05-03T22:14:28+00:00

When 'console=hvc0' is specified to the kernel parameter in x86 KVM guest,
hvc console is setup within a kthread. However, that will cause SEGV
and the boot will fail when the driver is builtin to the kernel,
because currently hvc_console_setup() is annotated with '__init'. This
patch removes '__init' to boot the guest successfully with 'console=hvc0'.

Signed-off-by: Tomoki Sekiyama 
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

n_tty: Fix n_tty_write crash when echoing in raw mode

2014-05-03T22:13:05+00:00

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

References: CVE-2014-0196
Reported-and-tested-by: Jiri Slaby 
Signed-off-by: Peter Hurley 
Signed-off-by: Jiri Slaby 
Cc: Linus Torvalds 
Cc: Alan Cox 
Cc: 
Signed-off-by: Greg Kroah-Hartman

tty: serial: 8250_core.c Bug fix for Exar chips.

2014-05-03T22:13:05+00:00

The sleep function was updated to put the serial port to sleep only when necessary.
This appears to resolve the errant behavior of the driver as described in
Kernel Bug 61961 – "My Exar Corp. XR17C/D152 Dual PCI UART modem does not
work with 3.8.0".

Signed-off-by: Michael Welling 
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

serial_core: fix uart PORT_UNKNOWN handling

2014-04-24T22:38:22+00:00

While porting a RS485 driver from 2.6.29 to 3.14, i noticed that the serial tty
driver could break it by using uart ports that it does not own :

1. uart_change_pm ist called during uart_open and calls the uart pm function
   without checking for PORT_UNKNOWN.
   The fix is to move uart_change_pm from uart_open to uart_port_startup.
2. The return code from the uart request_port call in uart_set_info is not
   handled properly, leading to the situation that the serial driver also
   thinks it owns the uart ports.
   This can triggered by doing following actions :

   setserial /dev/ttyS0 uart none    # release the uart ports
   modprobe lirc-serial              # or any other device that uses the uart
   setserial /dev/ttyS0 uart 16550   # gives no error and the uart tty driver
                                     # can use the ports as well

Signed-off-by: Thomas Pfaff 
Reviewed-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman

serial: samsung: Change barrier() to cpu_relax() in console output

2014-04-24T22:38:22+00:00

The two functions to write out to the console (one used in normal
console mode and one in polling console mode) were slightly different.
One used a barrier() in its loop and the other a cpu_relax().  The
barrier() really doesn't do anything since we're using rd_regl() to
read the port anyway.  Switch it to cpu_relax() to make things
consistent.

No known bugs / issues are fixed by this change--it just makes things
more consistent.

Signed-off-by: Doug Anderson 
Signed-off-by: Greg Kroah-Hartman

serial: samsung: don't check config for every character

2014-04-24T22:38:21+00:00

The s3c24xx_serial_console_putchar() is _only_ ever used by
s3c24xx_serial_console_write() and is called in a loop (indirectly
through uart_console_write()).  There's no reason to call
s3c24xx_port_configured() for every iteration through the loop.  Move
it outside the loop.

Signed-off-by: Doug Anderson 
Signed-off-by: Greg Kroah-Hartman

serial: samsung: Use the passed in "port", fixing kgdb w/ no console

2014-04-24T22:38:21+00:00

The two functions in the samsung serial driver used for writing
characters out to the port were inconsistent about whether they used
the passed in "port" or the global "cons_uart".  There was no reason
to use the global and the use of the global in
s3c24xx_serial_put_poll_char() caused a crash in the case where you
used the serial port for kgdboc but not for console.

Fix it so we used the passed in variable.

Note that this doesn't fix all problems with the samsung serial
driver.  Specifically:
* s3c24xx_serial_console_putchar() is still 99% identical to
  s3c24xx_serial_put_poll_char() (the function signature is different,
  but that's about it).  A future patch will make them slightly less
  identical and judging by other serial drivers we may need yet more
  differences eventually.
* The samsung serial driver still doesn't allow you to have more than
  one console port since it still uses the global cons_uart in
  s3c24xx_serial_console_write().

Signed-off-by: Doug Anderson 
Signed-off-by: Greg Kroah-Hartman