commit b2aba15ad6f908d1a620fd97f6af5620c3639742 upstream.

Currently, when kdb is compiled with keyboard support, then we will use
schedule_work() to provoke reset of the keyboard status.  Unfortunately
schedule_work() gets called from the kgdboc post-debug-exception
handler.  That risks deadlock since schedule_work() is not NMI-safe and,
even on platforms where the NMI is not directly used for debugging, the
debug trap can have NMI-like behaviour depending on where breakpoints
are placed.

Fix this by using the irq work system, which is NMI-safe, to defer the
call to schedule_work() to a point when it is safe to call.

Reported-by: Liuye <liu.yeC@h3c.com>
Closes: https://lore.kernel.org/all/20240228025602.3087748-1-liu.yeC@h3c.com/
Cc: stable@vger.kernel.org
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240424-kgdboc_fix_schedule_work-v2-1-50f5a490aec5@linaro.org
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 1aa4ad4eb695bac1b0a7ba542a16d6833c9c8dd8 upstream.

We are seeing start_tx being called after port shutdown as noted by Jiri.
This happens because we are missing the startup and shutdown related
functions for the serial base port.

Let's fix the issue by adding startup and shutdown functions for the
serial base port to block tx flushing for the serial base port when the
port is not in use.

Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
Cc: stable <stable@kernel.org>
Reported-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20240411055848.38190-1-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 9cf7ea2eeb745213dc2a04103e426b960e807940 upstream.

The circular buffer is NULLified in uart_tty_port_shutdown()
under the spin lock. However, the PM or other timer based callbacks
may still trigger after this event without knowning that buffer pointer
is not valid. Since the serial code is a bit inconsistent in checking
the buffer state (some rely on the head-tail positions, some on the
buffer pointer), it's better to have both aligned, i.e. buffer pointer
to be NULL and head-tail possitions to be the same, meaning it's empty.
This will prevent asynchronous calls to dereference NULL pointer as
reported recently in 8250 case:

  BUG: kernel NULL pointer dereference, address: 00000cf5
  Workqueue: pm pm_runtime_work
  EIP: serial8250_tx_chars (drivers/tty/serial/8250/8250_port.c:1809)
  ...
  ? serial8250_tx_chars (drivers/tty/serial/8250/8250_port.c:1809)
  __start_tx (drivers/tty/serial/8250/8250_port.c:1551)
  serial8250_start_tx (drivers/tty/serial/8250/8250_port.c:1654)
  serial_port_runtime_suspend (include/linux/serial_core.h:667 drivers/tty/serial/serial_port.c:63)
  __rpm_callback (drivers/base/power/runtime.c:393)
  ? serial_port_remove (drivers/tty/serial/serial_port.c:50)
  rpm_suspend (drivers/base/power/runtime.c:447)

The proposed change will prevent ->start_tx() to be called during
suspend on shut down port.

Fixes: 43066e32227e ("serial: port: Don't suspend if the port is still busy")
Cc: stable <stable@kernel.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202404031607.2e92eebe-lkp@intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240404150034.41648-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit ea2624b5b829b8f93c0dce25721d835969b34faf upstream.

When an UART is opened that still has .throttled set from a previous
open, the RX interrupt is enabled but the irq handler doesn't consider
it. This easily results in a stuck irq with the effect to occupy the CPU
in a tight loop.

So reset the throttle state in .startup() to ensure that RX irqs are
handled.

Fixes: d1ec8a2eabe9 ("serial: stm32: update throttle and unthrottle ops for dma mode")
Cc: stable@vger.kernel.org
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/a784f80d3414f7db723b2ec66efc56e1ad666cbf.1713344161.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 13c785323b36b845300b256d0e5963c3727667d7 upstream.

If there is a stuck irq that the handler doesn't address, returning
IRQ_HANDLED unconditionally makes it impossible for the irq core to
detect the problem and disable the irq. So only return IRQ_HANDLED if
an event was handled.

A stuck irq is still problematic, but with this change at least it only
makes the UART nonfunctional instead of occupying the (usually only) CPU
by 100% and so stall the whole machine.

Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")
Cc: stable@vger.kernel.org
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/5f92603d0dfd8a5b8014b2b10a902d91e0bb881f.1713344161.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 1be3226445362bfbf461c92a5bcdb1723f2e4907 upstream.

The mitigation was intended to stop the irq completely. That may be
better than a hard lock-up but it turns out that you get a crash anyway
if you're using pmac_zilog as a serial console:

ttyPZ0: pmz: rx irq flood !
BUG: spinlock recursion on CPU#0, swapper/0

That's because the pr_err() call in pmz_receive_chars() results in
pmz_console_write() attempting to lock a spinlock already locked in
pmz_interrupt(). With CONFIG_DEBUG_SPINLOCK=y, this produces a fatal
BUG splat. The spinlock in question is the one in struct uart_port.

Even when it's not fatal, the serial port rx function ceases to work.
Also, the iteration limit doesn't play nicely with QEMU, as can be
seen in the bug report linked below.

A web search for other reports of the error message "pmz: rx irq flood"
didn't produce anything. So I don't think this code is needed any more.
Remove it.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: stable@kernel.org
Cc: linux-m68k@lists.linux-m68k.org
Link: https://github.com/vivier/qemu-m68k/issues/44
Link: https://lore.kernel.org/all/1078874617.9746.36.camel@gaston/
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable@kernel.org>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Link: https://lore.kernel.org/r/e853cf2c762f23101cd2ddec0cc0c2be0e72685f.1712568223.git.fthain@linux-m68k.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 54c4ec5f8c471b7c1137a1f769648549c423c026 upstream.

The uart_handle_cts_change() function in serial_core expects the caller
to hold uport->lock. For example, I have seen the below kernel splat,
when the Bluetooth driver is loaded on an i.MX28 board.

    [   85.119255] ------------[ cut here ]------------
    [   85.124413] WARNING: CPU: 0 PID: 27 at /drivers/tty/serial/serial_core.c:3453 uart_handle_cts_change+0xb4/0xec
    [   85.134694] Modules linked in: hci_uart bluetooth ecdh_generic ecc wlcore_sdio configfs
    [   85.143314] CPU: 0 PID: 27 Comm: kworker/u3:0 Not tainted 6.6.3-00021-gd62a2f068f92 #1
    [   85.151396] Hardware name: Freescale MXS (Device Tree)
    [   85.156679] Workqueue: hci0 hci_power_on [bluetooth]
    (...)
    [   85.191765]  uart_handle_cts_change from mxs_auart_irq_handle+0x380/0x3f4
    [   85.198787]  mxs_auart_irq_handle from __handle_irq_event_percpu+0x88/0x210
    (...)

Cc: stable@vger.kernel.org
Fixes: 4d90bb147ef6 ("serial: core: Document and assert lock requirements for irq helpers")
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Emil Kronborg <emil.kronborg@protonmail.com>
Link: https://lore.kernel.org/r/20240320121530.11348-1-emil.kronborg@protonmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 3d9319c27ceb35fa3d2c8b15508967f3fc7e5b78 upstream.

This reverts commit 5c7e105cd156fc9adf5294a83623d7a40c15f9b9.

As identified by KASAN, the simplification done by the cleanup patch
was not legal.

>From tracing through the code, it can be seen that we're transmitting
from a 4096-byte circular buffer. We copy anywhere from 1-4 bytes from
it each time. The simplification runs into trouble when we get near
the end of the circular buffer. For instance, we might start out with
xmit->tail = 4094 and we want to transfer 4 bytes. With the code
before simplification this was no problem. We'd read buf[4094],
buf[4095], buf[0], and buf[1]. With the new code we'll do a
memcpy(&buf[4094], 4) which reads 2 bytes past the end of the buffer
and then skips transmitting what's at buf[0] and buf[1].

KASAN isn't 100% consistent at reporting this for me, but to be extra
confident in the analysis, I added traces of the tail and tx_bytes and
then wrote a test program:

  while true; do
    echo -n "abcdefghijklmnopqrstuvwxyz0" > /dev/ttyMSM0
    sleep .1
  done

I watched the traces over SSH and saw:
  qcom_geni_serial_send_chunk_fifo: 4093 4
  qcom_geni_serial_send_chunk_fifo: 1 3

Which indicated that one byte should be missing. Sure enough the
output that should have been:

  abcdefghijklmnopqrstuvwxyz0

In one case was actually missing a byte:

  abcdefghijklmnopqrstuvwyz0

Running "ls -al" on large directories also made the missing bytes
obvious since columns didn't line up.

While the original code may not be the most elegant, we only talking
about copying up to 4 bytes here. Let's just go back to the code that
worked.

Fixes: 5c7e105cd156 ("tty: serial: simplify qcom_geni_serial_send_chunk_fifo()")
Cc: stable <stable@kernel.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Jiri Slaby <jirislaby@kernel.org>
Tested-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20240304174952.1.I920a314049b345efd1f69d708e7f74d2213d0b49@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 1581dafaf0d34bc9c428a794a22110d7046d186d upstream.

This is the same issue that was fixed for the VGA text buffer in commit
39cdb68c64d8 ("vt: fix memory overlapping when deleting chars in the
buffer"). The cure is also the same i.e. replace memcpy() with memmove()
due to the overlaping buffers.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Fixes: 81732c3b2fed ("tty vt: Fix line garbage in virtual console on command line edition")
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/r/sn184on2-3p0q-0qrq-0218-895349s4753o@syhkavp.arg
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 43066e32227ecde674e8ae1fcdd4a1ede67680c2 upstream.

We accidently met the issue that the bash prompt is not shown after the
previous command done and until the next input if there's only one CPU
(In our issue other CPUs are isolated by isolcpus=). Further analysis
shows it's because the port entering runtime suspend even if there's
still pending chars in the buffer and the pending chars will only be
processed in next device resuming. We are using amba-pl011 and the
problematic flow is like below:

Bash                                         kworker
tty_write()
  file_tty_write()
    n_tty_write()
      uart_write()
        __uart_start()
          pm_runtime_get() // wakeup waker
            queue_work()
                                             pm_runtime_work()
                                               rpm_resume()
                                                status = RPM_RESUMING
                                                serial_port_runtime_resume()
                                                  port->ops->start_tx()
                                                    pl011_tx_chars()
                                                      uart_write_wakeup()
        […]
        __uart_start()
          pm_runtime_get() < 0 // because runtime status = RPM_RESUMING
                               // later data are not commit to the port driver
                                                status = RPM_ACTIVE
                                                rpm_idle() -> rpm_suspend()

This patch tries to fix this by checking the port busy before entering
runtime suspending. A runtime_suspend callback is added for the port
driver. When entering runtime suspend the callback is invoked, if there's
still pending chars in the buffer then flush the buffer.

Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
Cc: stable <stable@kernel.org>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lore.kernel.org/r/20240226152351.40924-1-yangyicong@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>