| 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
| ||
|
Message-Id: <20250414031450.42237-1-cuiyunhui@bytedance.com>
Date: Mon, 14 Apr 2025 11:14:50 +0800
From: Yunhui Cui <cuiyunhui@...edance.com>
To: ilpo.jarvinen@...ux.intel.com,
andriy.shevchenko@...ux.intel.com,
gregkh@...uxfoundation.org,
jirislaby@...nel.org,
john.ogness@...utronix.de,
pmladek@...e.com,
arnd@...db.de,
namcao@...utronix.de,
cuiyunhui@...edance.com,
benjamin.larsson@...exis.eu,
schnelle@...ux.ibm.com,
heikki.krogerus@...ux.intel.com,
markus.mayer@...aro.org,
tim.kryger@...aro.org,
matt.porter@...aro.org,
linux-kernel@...r.kernel.org,
linux-serial@...r.kernel.org
Subject: [PATCH v3] serial: 8250: fix panic due to PSLVERR
When the PSLVERR_RESP_EN parameter is set to 1, the device generates
an error response if an attempt is made to read an empty RBR (Receive
Buffer Register) while the FIFO is enabled.
In serial8250_do_startup(), calling serial_port_out(port, UART_LCR,
UART_LCR_WLEN8) triggers dw8250_check_lcr(), which invokes
dw8250_force_idle() and serial8250_clear_and_reinit_fifos(). The latter
function enables the FIFO via serial_out(p, UART_FCR, p->fcr).
Execution proceeds to the dont_test_tx_en label:
...
serial_port_in(port, UART_RX);
This satisfies the PSLVERR trigger condition.
Because another CPU(e.g., using printk()) is accessing the UART (UART
is busy), the current CPU fails the check (value & ~UART_LCR_SPAR) ==
(lcr & ~UART_LCR_SPAR), causing it to enter dw8250_force_idle().
To fix this, all calls to serial_out(UART_LCR) and serial_in(UART_RX)
should be executed under port->lock. Additionally, checking the readiness
via UART_LSR should also be done under port->lock.
Panic backtrace:
[ 0.442336] Oops - unknown exception [#1]
[ 0.442343] epc : dw8250_serial_in32+0x1e/0x4a
[ 0.442351] ra : serial8250_do_startup+0x2c8/0x88e
...
[ 0.442416] console_on_rootfs+0x26/0x70
Fixes: c49436b657d0 ("serial: 8250_dw: Improve unwritable LCR workaround")
Link: https://lore.kernel.org/all/84cydt5peu.fsf@jogness.linutronix.de/T/
Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
---
drivers/tty/serial/8250/8250_dw.c | 8 +++++
drivers/tty/serial/8250/8250_port.c | 46 ++++++++++++++++++-----------
2 files changed, 36 insertions(+), 18 deletions(-)
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index af24ec25d976..e97200ff30e3 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -13,6 +13,7 @@
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/io.h>
+#include <linux/lockdep.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/notifier.h>
@@ -112,6 +113,13 @@ static void dw8250_force_idle(struct uart_port *p)
struct uart_8250_port *up = up_to_u8250p(p);
unsigned int lsr;
+ /*
+ * Serial_in(p, UART_RX) should be under port->lock, but we can't add
+ * it to avoid AA deadlock as we're unsure if serial_out*(...UART_LCR)
+ * is under port->lock.
+ */
+ lockdep_assert_held_once(&p->lock);
+
serial8250_clear_and_reinit_fifos(up);
/*
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 3f256e96c722..21bbd18195f5 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1328,6 +1328,7 @@ static void autoconfig_irq(struct uart_8250_port *up)
unsigned int ICP = 0;
unsigned long irqs;
int irq;
+ u16 lsr;
if (port->flags & UPF_FOURPORT) {
ICP = (port->iobase & 0xfe0) | 0x1f;
@@ -1357,9 +1358,10 @@ static void autoconfig_irq(struct uart_8250_port *up)
/* Synchronize UART_IER access against the console. */
uart_port_lock_irq(port);
serial_out(up, UART_IER, UART_IER_ALL_INTR);
+ lsr = serial_in(up, UART_LSR);
+ if (lsr & UART_LSR_DR)
+ serial_port_in(port, UART_RX);
uart_port_unlock_irq(port);
- serial_in(up, UART_LSR);
- serial_in(up, UART_RX);
serial_in(up, UART_IIR);
serial_in(up, UART_MSR);
serial_out(up, UART_TX, 0xFF);
@@ -2137,19 +2139,16 @@ static void wait_for_xmitr(struct uart_8250_port *up, int bits)
static int serial8250_get_poll_char(struct uart_port *port)
{
struct uart_8250_port *up = up_to_u8250p(port);
- int status;
+ int status = NO_POLL_CHAR;
u16 lsr;
serial8250_rpm_get(up);
+ uart_port_lock_irqsave(port, &flags);
lsr = serial_port_in(port, UART_LSR);
-
- if (!(lsr & UART_LSR_DR)) {
- status = NO_POLL_CHAR;
- goto out;
- }
-
- status = serial_port_in(port, UART_RX);
+ if ((lsr & UART_LSR_DR))
+ status = serial_port_in(port, UART_RX);
+ uart_port_unlock_irqrestore(port, flags);
out:
serial8250_rpm_put(up);
return status;
@@ -2264,13 +2263,16 @@ int serial8250_do_startup(struct uart_port *port)
* Clear the FIFO buffers and disable them.
* (they will be reenabled in set_termios())
*/
+ uart_port_lock_irqsave(port, &flags);
serial8250_clear_fifos(up);
/*
* Clear the interrupt registers.
*/
- serial_port_in(port, UART_LSR);
- serial_port_in(port, UART_RX);
+ lsr = serial_port_in(port, UART_LSR);
+ if (lsr & UART_LSR_DR)
+ serial_port_in(port, UART_RX);
+ uart_port_unlock_irqrestore(port, flags);
serial_port_in(port, UART_IIR);
serial_port_in(port, UART_MSR);
@@ -2380,9 +2382,10 @@ int serial8250_do_startup(struct uart_port *port)
/*
* Now, initialize the UART
*/
- serial_port_out(port, UART_LCR, UART_LCR_WLEN8);
uart_port_lock_irqsave(port, &flags);
+ serial_port_out(port, UART_LCR, UART_LCR_WLEN8);
+
if (up->port.flags & UPF_FOURPORT) {
if (!up->port.irq)
up->port.mctrl |= TIOCM_OUT1;
@@ -2428,15 +2431,16 @@ int serial8250_do_startup(struct uart_port *port)
}
dont_test_tx_en:
- uart_port_unlock_irqrestore(port, flags);
/*
* Clear the interrupt registers again for luck, and clear the
* saved flags to avoid getting false values from polling
* routines or the previous session.
*/
- serial_port_in(port, UART_LSR);
- serial_port_in(port, UART_RX);
+ lsr = serial_port_in(port, UART_LSR);
+ if (lsr & UART_LSR_DR)
+ serial_port_in(port, UART_RX);
+ uart_port_unlock_irqrestore(port, flags);
serial_port_in(port, UART_IIR);
serial_port_in(port, UART_MSR);
up->lsr_saved_flags = 0;
@@ -2492,6 +2496,7 @@ void serial8250_do_shutdown(struct uart_port *port)
{
struct uart_8250_port *up = up_to_u8250p(port);
unsigned long flags;
+ u16 lsr;
serial8250_rpm_get(up);
/*
@@ -2518,7 +2523,6 @@ void serial8250_do_shutdown(struct uart_port *port)
port->mctrl &= ~TIOCM_OUT2;
serial8250_set_mctrl(port, port->mctrl);
- uart_port_unlock_irqrestore(port, flags);
/*
* Disable break condition and FIFOs
@@ -2526,6 +2530,7 @@ void serial8250_do_shutdown(struct uart_port *port)
serial_port_out(port, UART_LCR,
serial_port_in(port, UART_LCR) & ~UART_LCR_SBC);
serial8250_clear_fifos(up);
+ uart_port_unlock_irqrestore(port, flags);
#ifdef CONFIG_SERIAL_8250_RSA
/*
@@ -2538,7 +2543,12 @@ void serial8250_do_shutdown(struct uart_port *port)
* Read data port to reset things, and then unlink from
* the IRQ chain.
*/
- serial_port_in(port, UART_RX);
+ uart_port_lock_irqsave(port, &flags);
+ lsr = serial_port_in(port, UART_LSR);
+ if (lsr & UART_LSR_DR)
+ serial_port_in(port, UART_RX);
+ uart_port_unlock_irqrestore(port, flags);
+
serial8250_rpm_put(up);
up->ops->release_irq(up);
--
2.39.2
Powered by blists - more mailing lists