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linux/drivers/tty/serial
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John Keeping 5e00346deb serial: 8250: Fix fifo underflow on flush 
commit 9e512eaaf8 upstream.

When flushing the serial port's buffer, uart_flush_buffer() calls
kfifo_reset() but if there is an outstanding DMA transfer then the
completion function will consume data from the kfifo via
uart_xmit_advance(), underflowing and leading to ongoing DMA as the
driver tries to transmit another 2^32 bytes.

This is readily reproduced with serial-generic and amidi sending even
short messages as closing the device on exit will wait for the fifo to
drain and in the underflow case amidi hangs for 30 seconds on exit in
tty_wait_until_sent().  A trace of that gives:

     kworker/1:1-84    [001]    51.769423: bprint:               serial8250_tx_dma: tx_size=3 fifo_len=3
           amidi-763   [001]    51.769460: bprint:               uart_flush_buffer: resetting fifo
 irq/21-fe530000-76    [000]    51.769474: bprint:               __dma_tx_complete: tx_size=3
 irq/21-fe530000-76    [000]    51.769479: bprint:               serial8250_tx_dma: tx_size=4096 fifo_len=4294967293
 irq/21-fe530000-76    [000]    51.781295: bprint:               __dma_tx_complete: tx_size=4096
 irq/21-fe530000-76    [000]    51.781301: bprint:               serial8250_tx_dma: tx_size=4096 fifo_len=4294963197
 irq/21-fe530000-76    [000]    51.793131: bprint:               __dma_tx_complete: tx_size=4096
 irq/21-fe530000-76    [000]    51.793135: bprint:               serial8250_tx_dma: tx_size=4096 fifo_len=4294959101
 irq/21-fe530000-76    [000]    51.804949: bprint:               __dma_tx_complete: tx_size=4096

Since the port lock is held in when the kfifo is reset in
uart_flush_buffer() and in __dma_tx_complete(), adding a flush_buffer
hook to adjust the outstanding DMA byte count is sufficient to avoid the
kfifo underflow.

Fixes: 9ee4b83e51 ("serial: 8250: Add support for dmaengine")
Cc: stable <stable@kernel.org>
Signed-off-by: John Keeping <jkeeping@inmusicbrands.com>
Link: https://lore.kernel.org/r/20250208124148.1189191-1-jkeeping@inmusicbrands.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-02-21 13:57:18 +01:00
..
8250 serial: 8250: Fix fifo underflow on flush 2025-02-21 13:57:18 +01:00
jsm drivers: serial: jsm: fix some leaks in probe 2022-09-22 16:11:43 +02:00
21285.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
altera_jtaguart.c serial: altera_jtaguart: switch status to u32 2023-07-31 17:16:05 +02:00
altera_uart.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
amba-pl010.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
amba-pl011.c serial: amba-pl011: fix build regression 2024-12-14 20:00:23 +01:00
apbuart.c serial: apbuart: fix console prompt on qemu 2024-01-25 15:35:55 -08:00
apbuart.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
ar933x_uart.c serial: ar933x: Use devm_platform_get_and_ioremap_resource() 2023-07-25 20:25:52 +02:00
arc_uart.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
atmel_serial.c tty: atmel_serial: use the correct RTS flag. 2024-08-29 17:33:10 +02:00
atmel_serial.h tty: serial: atmel: Use FIELD_PREP/FIELD_GET 2022-09-22 16:32:25 +02:00
bcm63xx_uart.c serial: bcm63xx-uart: fix tx after conversion to uart_port_tx_limited() 2024-07-05 09:34:00 +02:00
clps711x.c serial: clps711x: Use devm_platform_get_and_ioremap_resource() 2023-07-25 20:25:52 +02:00
cpm_uart.c serial: cpm_uart: Remove cpm_uart/ subdirectory 2023-08-04 15:08:30 +02:00
cpm_uart.h serial: cpm_uart: Remove cpm_uart/ subdirectory 2023-08-04 15:08:30 +02:00
digicolor-usart.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
dz.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
dz.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
earlycon-riscv-sbi.c serial: make uart_console_write->putchar()'s character an unsigned char 2022-03-03 15:06:31 +01:00
earlycon-semihost.c serial: Rename earlycon semihost driver 2023-01-19 14:58:19 +01:00
earlycon.c earlycon: Let users set the clock frequency 2023-01-19 14:56:44 +01:00
fsl_linflexuart.c serial: linflexuart: Use devm_platform_get_and_ioremap_resource() 2023-07-25 20:25:52 +02:00
fsl_lpuart.c tty: serial: fsl_lpuart: mark last busy before uart_add_one_port 2024-08-29 17:33:10 +02:00
icom.c serial: Make ->set_termios() old ktermios const 2022-08-30 14:22:35 +02:00
imx.c serial: imx: Update mctrl old_status on RTSD interrupt 2024-10-22 15:46:33 +02:00
imx_earlycon.c serial: make uart_console_write->putchar()'s character an unsigned char 2022-03-03 15:06:31 +01:00
ip22zilog.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
ip22zilog.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig TTY/Serial driver updates for 6.5-rc1. 2023-07-03 13:14:58 -07:00
kgdb_nmi.c tty: make tty_operations::write()'s count size_t 2023-08-11 21:12:46 +02:00
kgdboc.c serial: kgdboc: Fix NMI-safety problems from keyboard reset code 2024-05-25 16:22:54 +02:00
lantiq.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
liteuart.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
lpc32xx_hs.c tty: serial: use uart_port_tx() helper 2022-11-03 03:32:40 +01:00
ma35d1_serial.c tty: serial: ma35d1: Add a NULL check for of_node 2024-07-18 13:21:21 +02:00
Makefile serial: cpm_uart: Remove cpm_uart/ subdirectory 2023-08-04 15:08:30 +02:00
max310x.c serial: max310x: fix NULL pointer dereference in I2C instantiation 2024-04-03 15:28:16 +02:00
max3100.c serial: max3100: Fix bitwise types 2024-06-12 11:12:17 +02:00
mcf.c tty: mcf: MCF54418 has 10 UARTS 2024-07-05 09:34:00 +02:00
men_z135_uart.c serial: men_z135_uart: Use uart_xmit_advance() 2022-11-03 03:35:41 +01:00
meson_uart.c tty: serial: meson: fix hard LOCKUP on crtscts mode 2023-11-28 17:19:57 +00:00
milbeaut_usio.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
mpc52xx_uart.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
mps2-uart.c serial: mps2-uart: Use devm_platform_get_and_ioremap_resource() 2023-07-25 20:26:06 +02:00
msm_serial.c serial: msm: add lock annotation to msm_set_baud_rate() 2023-01-19 15:53:09 +01:00
mux.c tty: serial: use uart_port_tx_limited() 2022-11-03 03:32:40 +01:00
mvebu-uart.c serial: mvebu-uart: Use devm_platform_get_and_ioremap_resource() 2023-07-25 20:26:07 +02:00
mxs-auart.c serial: mxs-auart: add spinlock around changing cts state 2024-04-27 17:11:39 +02:00
omap-serial.c serial: omap: do not override settings for RS485 support 2024-01-25 15:35:44 -08:00
owl-uart.c tty: serial: use uart_port_tx() helper 2022-11-03 03:32:40 +01:00
pch_uart.c tty: pcn_uart: fix memory leak with using debugfs_lookup() 2023-02-08 13:09:55 +01:00
pic32_uart.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
pmac_zilog.c serial/pmac_zilog: Remove flawed mitigation for rx irq flood 2024-04-27 17:11:39 +02:00
pmac_zilog.h serial: pmac_zilog: remove unused uart_pmac_port::termios_cache 2022-05-19 18:23:19 +02:00
pxa.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
qcom_geni_serial.c serial: qcom-geni: fix receiver enable 2024-10-22 15:46:35 +02:00
rda-uart.c serial: rda: Use uart_xmit_advance() 2022-11-03 03:35:42 +01:00
rp2.c tty: rp2: Fix reset with non forgiving PCIe host bridges 2024-10-04 16:29:51 +02:00
sa1100.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
samsung_tty.c tty: serial: samsung: fix tx_empty() to return TIOCSER_TEMT 2024-03-26 18:20:05 -04:00
sb1250-duart.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
sc16is7xx.c serial: sc16is7xx: use device_property APIs when configuring irda mode 2025-02-08 09:51:50 +01:00
sccnxp.c serial: sccnxp: Use devm_platform_get_and_ioremap_resource() 2023-07-25 20:26:07 +02:00
serial-tegra.c serial: tegra: handle clk prepare error in tegra_uart_hw_init() 2023-08-22 15:29:18 +02:00
serial_base.h serial: core: Fix missing shutdown and startup for serial base port 2024-04-27 17:11:39 +02:00
serial_base_bus.c serial: core: Fix serial core port id, including multiport devices 2023-08-11 21:19:22 +02:00
serial_core.c serial: protect uart_port_dtr_rts() in uart_shutdown() too 2024-10-17 15:24:19 +02:00
serial_ctrl.c serial: core: Start managing serial controllers to enable runtime PM 2023-05-31 10:46:59 +01:00
serial_mctrl_gpio.c Documentation: serial: move GPIO kernel-doc to the functions 2022-07-28 10:37:42 +02:00
serial_mctrl_gpio.h serial: mctrl_gpio: add a new API to enable / disable wake_irq 2022-02-08 11:07:16 +01:00
serial_port.c serial: port: Always update ->iotype in __uart_read_properties() 2025-02-21 13:57:18 +01:00
serial_txx9.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
sh-sci.c serial: sh-sci: Do not probe the serial port if its slot in sci_ports[] is in use 2025-02-17 09:40:24 +01:00
sh-sci.h tty: serial: sh-sci: Add support for tx end interrupt handling 2023-04-20 13:47:33 +02:00
sifive.c serial: sifive: Add suspend and resume operations 2023-08-22 15:29:10 +02:00
sprd_serial.c serial: sprd: Fix DMA buffer leak issue 2023-07-30 13:53:55 +02:00
st-asc.c drivers:tty: fix return value check in asc_init_port 2023-07-30 13:53:19 +02:00
stm32-usart.c serial: stm32: Reset .throttled state in .startup() 2024-04-27 17:11:39 +02:00
stm32-usart.h serial: stm32: group dma pause/resume error handling into single function 2023-08-22 15:28:51 +02:00
suncore.c tty: Use of_node_name_{eq,prefix} for node name comparisons 2018-12-17 16:12:17 +01:00
sunhv.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
sunplus-uart.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
sunsab.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
sunsab.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
sunsu.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
sunzilog.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
sunzilog.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
tegra-tcu.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
timbuart.c serial: timbuart: Use uart_xmit_advance() 2022-11-03 03:35:43 +01:00
timbuart.h tty: serial: Use the correct style for SPDX License Identifier 2020-03-07 09:52:01 +01:00
uartlite.c tty: Explicitly include correct DT includes 2023-07-25 20:19:05 +02:00
ucc_uart.c serial: cpm_uart: Don't include fs_uart_pd.h when not needed 2023-08-04 15:08:55 +02:00
vt8500_serial.c serial: vt8500: Use devm_platform_get_and_ioremap_resource() 2023-07-25 20:26:06 +02:00
xilinx_uartps.c tty: xilinx_uartps: split sysrq handling 2025-02-17 09:40:43 +01:00
zs.c serial: drivers: switch ch and flag to u8 2023-07-25 19:21:04 +02:00
zs.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00