linux-kernel - [PATCH v4 4/4] serial: 8250_dw: fix PSLVERR on RX

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250425062425.68761-4-cuiyunhui@bytedance.com>
Date: Fri, 25 Apr 2025 14:24:25 +0800
From: Yunhui Cui <cuiyunhui@...edance.com>
To: arnd@...db.de,
	andriy.shevchenko@...ux.intel.com,
	benjamin.larsson@...exis.eu,
	cuiyunhui@...edance.com,
	gregkh@...uxfoundation.org,
	heikki.krogerus@...ux.intel.com,
	ilpo.jarvinen@...ux.intel.com,
	jirislaby@...nel.org,
	jkeeping@...usicbrands.com,
	john.ogness@...utronix.de,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	markus.mayer@...aro.org,
	matt.porter@...aro.org,
	namcao@...utronix.de,
	paulmck@...nel.org,
	pmladek@...e.com,
	schnelle@...ux.ibm.com,
	sunilvl@...tanamicro.com,
	tim.kryger@...aro.org
Subject: [PATCH v4 4/4] serial: 8250_dw: fix PSLVERR on RX_TIMEOUT

In the case of RX_TIMEOUT, to avoid PSLVERR, disable the FIFO
before reading UART_RX when UART_LSR_DR is not set.

Fixes: 424d79183af0 ("serial: 8250_dw: Avoid "too much work" from bogus rx timeout interrupt")
Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
---
 drivers/tty/serial/8250/8250_dw.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 07f9be074b4b..1e364280a108 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -273,6 +273,7 @@ static int dw8250_handle_irq(struct uart_port *p)
 	unsigned int quirks = d->pdata->quirks;
 	unsigned int status;
 	unsigned long flags;
+	unsigned char old_fcr;
 
 	/*
 	 * There are ways to get Designware-based UARTs into a state where
@@ -288,9 +289,19 @@ static int dw8250_handle_irq(struct uart_port *p)
 		uart_port_lock_irqsave(p, &flags);
 		status = serial_lsr_in(up);
 
-		if (!(status & (UART_LSR_DR | UART_LSR_BI)))
+		if (!(status & (UART_LSR_DR | UART_LSR_BI))) {
+			/* To avoid PSLVERR, disable the FIFO first. */
+			if (up->fcr & UART_FCR_ENABLE_FIFO) {
+				old_fcr = serial_in(up, UART_FCR);
+				serial_out(up, UART_FCR, old_fcr & ~1);
+			}
+
 			(void) p->serial_in(p, UART_RX);
 
+			if (up->fcr & UART_FCR_ENABLE_FIFO)
+				serial_out(up, UART_FCR, old_fcr);
+		}
+
 		uart_port_unlock_irqrestore(p, flags);
 	}
 
-- 
2.39.2