linux.git/drivers/tty, branch v6.1.92

serial: kgdboc: Fix NMI-safety problems from keyboard reset code

2024-05-25T14:21:35+00:00

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

serial: stm32: Reset .throttled state in .startup()

2024-04-27T15:07:14+00:00

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 
Link: https://lore.kernel.org/r/a784f80d3414f7db723b2ec66efc56e1ad666cbf.1713344161.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman

serial: stm32: Return IRQ_NONE in the ISR if no handling happend

2024-04-27T15:07:14+00:00

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 
Link: https://lore.kernel.org/r/5f92603d0dfd8a5b8014b2b10a902d91e0bb881f.1713344161.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman

serial/pmac_zilog: Remove flawed mitigation for rx irq flood

2024-04-27T15:07:14+00:00

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 
Cc: Michael Ellerman 
Cc: Nicholas Piggin 
Cc: Christophe Leroy 
Cc: Aneesh Kumar K.V 
Cc: Naveen N. Rao 
Cc: Andy Shevchenko 
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 
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable 
Signed-off-by: Finn Thain 
Link: https://lore.kernel.org/r/e853cf2c762f23101cd2ddec0cc0c2be0e72685f.1712568223.git.fthain@linux-m68k.org
Signed-off-by: Greg Kroah-Hartman

serial: mxs-auart: add spinlock around changing cts state

2024-04-27T15:07:14+00:00

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 
Signed-off-by: Emil Kronborg 
Link: https://lore.kernel.org/r/20240320121530.11348-1-emil.kronborg@protonmail.com
Signed-off-by: Greg Kroah-Hartman

tty: n_gsm: require CAP_NET_ADMIN to attach N_GSM0710 ldisc

2024-04-13T11:05:23+00:00

commit 67c37756898a5a6b2941a13ae7260c89b54e0d88 upstream.

Any unprivileged user can attach N_GSM0710 ldisc, but it requires
CAP_NET_ADMIN to create a GSM network anyway.

Require initial namespace CAP_NET_ADMIN to do that.

Signed-off-by: Thadeu Lima de Souza Cascardo 
Link: https://lore.kernel.org/r/20230731185942.279611-1-cascardo@canonical.com
Cc: Salvatore Bonaccorso 
Signed-off-by: Greg Kroah-Hartman

tty: serial: imx: Fix broken RS485

2024-04-03T13:19:46+00:00

commit 672448ccf9b6a676f96f9352cbf91f4d35f4084a upstream.

When about to transmit the function imx_uart_start_tx is called and in
some RS485 configurations this function will call imx_uart_stop_rx. The
problem is that imx_uart_stop_rx will enable loopback in order to
release the RS485 bus, but when loopback is enabled transmitted data
will just be looped to RX.

This patch fixes the above problem by not enabling loopback when about
to transmit.

This driver now works well when used for RS485 half duplex master
configurations.

Fixes: 79d0224f6bf2 ("tty: serial: imx: Handle RS485 DE signal active high")
Cc: stable 
Signed-off-by: Rickard x Andersson 
Tested-by: Christoph Niedermaier 
Link: https://lore.kernel.org/r/20240221115304.509811-1-rickaran@axis.com
Signed-off-by: Christoph Niedermaier 
Signed-off-by: Greg Kroah-Hartman

vt: fix unicode buffer corruption when deleting characters

2024-04-03T13:19:42+00:00

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

tty: serial: fsl_lpuart: avoid idle preamble pending if CTS is enabled

2024-04-03T13:19:41+00:00

commit 74cb7e0355fae9641f825afa389d3fba3b617714 upstream.

If the remote uart device is not connected or not enabled after booting
up, the CTS line is high by default. At this time, if we enable the flow
control when opening the device(for example, using “stty -F /dev/ttyLP4
crtscts” command), there will be a pending idle preamble(first writing 0
and then writing 1 to UARTCTRL_TE will queue an idle preamble) that
cannot be sent out, resulting in the uart port fail to close(waiting for
TX empty), so the user space stty will have to wait for a long time or
forever.

This is an LPUART IP bug(idle preamble has higher priority than CTS),
here add a workaround patch to enable TX CTS after enabling UARTCTRL_TE,
so that the idle preamble does not get stuck due to CTS is deasserted.

Fixes: 380c966c093e ("tty: serial: fsl_lpuart: add 32-bit register interface support")
Cc: stable 
Signed-off-by: Sherry Sun 
Reviewed-by: Alexander Sverdlin 
Link: https://lore.kernel.org/r/20240305015706.1050769-1-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman

serial: Lock console when calling into driver before registration

2024-04-03T13:19:31+00:00

[ Upstream commit 801410b26a0e8b8a16f7915b2b55c9528b69ca87 ]

During the handoff from earlycon to the real console driver, we have
two separate drivers operating on the same device concurrently. In the
case of the 8250 driver these concurrent accesses cause problems due
to the driver's use of banked registers, controlled by LCR.DLAB. It is
possible for the setup(), config_port(), pm() and set_mctrl() callbacks
to set DLAB, which can cause the earlycon code that intends to access
TX to instead access DLL, leading to missed output and corruption on
the serial line due to unintended modifications to the baud rate.

In particular, for setup() we have:

univ8250_console_setup()
-> serial8250_console_setup()
-> uart_set_options()
-> serial8250_set_termios()
-> serial8250_do_set_termios()
-> serial8250_do_set_divisor()

For config_port() we have:

serial8250_config_port()
-> autoconfig()

For pm() we have:

serial8250_pm()
-> serial8250_do_pm()
-> serial8250_set_sleep()

For set_mctrl() we have (for some devices):

serial8250_set_mctrl()
-> omap8250_set_mctrl()
-> __omap8250_set_mctrl()

To avoid such problems, let's make it so that the console is locked
during pre-registration calls to these callbacks, which will prevent
the earlycon driver from running concurrently.

Remove the partial solution to this problem in the 8250 driver
that locked the console only during autoconfig_irq(), as this would
result in a deadlock with the new approach. The console continues
to be locked during autoconfig_irq() because it can only be called
through uart_configure_port().

Although this patch introduces more locking than strictly necessary
(and in particular it also locks during the call to rs485_config()
which is not affected by this issue as far as I can tell), it follows
the principle that it is the responsibility of the generic console
code to manage the earlycon handoff by ensuring that earlycon and real
console driver code cannot run concurrently, and not the individual
drivers.

Signed-off-by: Peter Collingbourne 
Reviewed-by: John Ogness 
Link: https://linux-review.googlesource.com/id/I7cf8124dcebf8618e6b2ee543fa5b25532de55d8
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240304214350.501253-1-pcc@google.com
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin