Re: [PATCH 6.6] serial: sc16is7xx: fix invalid FIFO access with special register set

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

The upstream commit SHA1 provided is correct: 7d3b793faaab1305994ce568b59d61927235f57b

WARNING: Author mismatch between patch and upstream commit:
Backport author: Bin Lan <bin.lan.cn@windriver.com>
Commit author: Hugo Villeneuve <hvilleneuve@dimonoff.com>


Status in newer kernel trees:
6.12.y | Present (exact SHA1)
6.11.y | Present (exact SHA1)
6.6.y | Present (different SHA1: 19c41869465c)

Note: The patch differs from the upstream commit:
---
--- -	2024-11-25 21:31:42.179789487 -0500
+++ /tmp/tmp.38G55Mxp3K	2024-11-25 21:31:42.172164427 -0500
@@ -1,3 +1,5 @@
+[ Upstream commit 7d3b793faaab1305994ce568b59d61927235f57b ]
+
 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
@@ -22,25 +24,27 @@
 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>
+[ Resolve minor conflicts ]
+Signed-off-by: Bin Lan <bin.lan.cn@windriver.com>
 ---
  drivers/tty/serial/sc16is7xx.c | 4 ++++
  1 file changed, 4 insertions(+)
 
 diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
-index 58696e05492ca..b4c1798a1df2a 100644
+index 7a9924d9b294..d7728920853e 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)
+@@ -545,6 +545,8 @@ 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);
++	
+ 	/* Open the LCR divisors for configuration */
  	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_LCR_CONF_MODE_A);
+@@ -558,6 +560,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
+ 	/* Put LCR back to the normal mode */
  	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
  
 +	mutex_unlock(&one->efr_lock);
@@ -48,3 +52,6 @@
  	return DIV_ROUND_CLOSEST((clk / prescaler) / 16, div);
  }
  
+-- 
+2.34.1
+
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.6.y        |  Success    |  Success   |