I was puzzled while looking at /proc/interrupts and random things showed
up between reboots. This occurred more often but I realised it later. The
"correct" output should be:
|38: 11861 atmel-aic5 2 Level ttyS0
but I saw sometimes
|38: 6426 atmel-aic5 2 Level tty1
and accounted it wrongly as correct. This is use after free and the
former example randomly got the "old" pointer which pointed to the same
content. With SLAB_FREELIST_RANDOM and HARDENED I even got
|38: 7067 atmel-aic5 2 Level E=Started User Manager for UID 0
or other nonsense.
As it turns out the tty, pointer that is accessed in atmel_startup(), is
freed() before atmel_shutdown(). It seems to happen quite often that the
tty for ttyS0 is allocated and freed while ->shutdown is not invoked. I
don't do anything special - just a systemd boot :)
Use port->name as the IRQ name for request_irq(). This exists as long as
the driver is loaded so no use-after-free here.
For backports before v4.12 I suggest to use `"atmel_serial"' instead
`port->name' (that member was introduced in f7048b15900f ("tty: serial_core:
Add name field to uart_port struct").
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
v1…v2: - Bisected and added a Fixes tag
- added a note for backporters to v4.9 … v4.12 (pointed out by
Richard Genoud)
drivers/tty/serial/atmel_serial.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index e287fe8f10fc..d3189816740e 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1757,7 +1757,6 @@ static int atmel_startup(struct uart_port *port)
{
struct platform_device *pdev = to_platform_device(port->dev);
struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
- struct tty_struct *tty = port->state->port.tty;
int retval;
/*
@@ -1772,8 +1771,7 @@ static int atmel_startup(struct uart_port *port)
* Allocate the IRQ
*/
retval = request_irq(port->irq, atmel_interrupt,
- IRQF_SHARED | IRQF_COND_SUSPEND,
- tty ? tty->name : "atmel_serial", port);
+ IRQF_SHARED | IRQF_COND_SUSPEND, port->name, port);
if (retval) {
dev_err(port->dev, "atmel_startup - Can't get irq\n");
return retval;
--
2.17.0
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