The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 7d3b793faaab1305994ce568b59d61927235f57b # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024081204-deserving-flanked-a918@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

7d3b793faaab ("serial: sc16is7xx: fix invalid FIFO access with special register set") 8492bd91aa05 ("serial: sc16is7xx: fix bug in sc16is7xx_set_baud() when using prescaler") 0c84bea0cabc ("serial: sc16is7xx: refactor EFR lock") 2de8a1b46756 ("serial: sc16is7xx: reorder code to remove prototype declarations") 2e57cefc4477 ("serial: sc16is7xx: replace hardcoded divisor value with BIT() macro") 4409df5866b7 ("serial: sc16is7xx: change EFR lock to operate on each channels") 3837a0379533 ("serial: sc16is7xx: improve regmap debugfs by using one regmap per port") 22a048b07493 ("serial: sc16is7xx: remove unused to_sc16is7xx_port macro") b4a778303ea0 ("serial: sc16is7xx: add missing support for rs485 devicetree properties") 049994292834 ("serial: sc16is7xx: fix regression with GPIO configuration") dabc54a45711 ("serial: sc16is7xx: remove obsolete out_thread label") c8f71b49ee4d ("serial: sc16is7xx: setup GPIO controller later in probe")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7d3b793faaab1305994ce568b59d61927235f57b Mon Sep 17 00:00:00 2001 From: Hugo Villeneuve hvilleneuve@dimonoff.com Date: Tue, 23 Jul 2024 08:53:01 -0400 Subject: [PATCH] serial: sc16is7xx: fix invalid FIFO access with special register set

When enabling access to the special register set, Receiver time-out and RHR interrupts can happen. In this case, the IRQ handler will try to read from the FIFO thru the RHR register at address 0x00, but address 0x00 is mapped to DLL register, resulting in erroneous FIFO reading.

Call graph example: sc16is7xx_startup(): entry sc16is7xx_ms_proc(): entry sc16is7xx_set_termios(): entry sc16is7xx_set_baud(): DLH/DLL = $009C --> access special register set sc16is7xx_port_irq() entry --> IIR is 0x0C sc16is7xx_handle_rx() entry sc16is7xx_fifo_read(): --> unable to access FIFO (RHR) because it is mapped to DLL (LCR=LCR_CONF_MODE_A) sc16is7xx_set_baud(): exit --> Restore access to general register set

Fix the problem by claiming the efr_lock mutex when accessing the Special register set.

Fixes: dfeae619d781 ("serial: sc16is7xx") Cc: stable@vger.kernel.org Signed-off-by: Hugo Villeneuve hvilleneuve@dimonoff.com Link: https://lore.kernel.org/r/20240723125302.1305372-3-hugo@hugovil.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c index 58696e05492c..b4c1798a1df2 100644 --- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -592,6 +592,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud) SC16IS7XX_MCR_CLKSEL_BIT, prescaler == 1 ? 0 : SC16IS7XX_MCR_CLKSEL_BIT);

+ mutex_lock(&one->efr_lock); + /* Backup LCR and access special register set (DLL/DLH) */ lcr = sc16is7xx_port_read(port, SC16IS7XX_LCR_REG); sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, @@ -606,6 +608,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud) /* Restore LCR and access to general register set */ sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);

+ mutex_unlock(&one->efr_lock); + return DIV_ROUND_CLOSEST((clk / prescaler) / 16, div); }