2022-05-09 04:44:02

by John Ogness

Subject: [PATCH next v1] serial: msm_serial: disable interrupts in __msm_console_write()

__msm_console_write() assumes that interrupts are disabled, but
with threaded console printers it is possible that the write()
callback of the console is called with interrupts enabled.

Explicitly disable interrupts using local_irq_save() to preserve
the assumed context.

Reported-by: Marek Szyprowski <[email protected]>
Signed-off-by: John Ogness <[email protected]>
---
Note: I checked the other serial drivers and this was the only
one that assumed interrupts off for write().

drivers/tty/serial/msm_serial.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 23c94b927776..e676ec761f18 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -1599,6 +1599,7 @@ static inline struct uart_port *msm_get_port_from_line(unsigned int line)
static void __msm_console_write(struct uart_port *port, const char *s,
unsigned int count, bool is_uartdm)
{
+ unsigned long flags;
int i;
int num_newlines = 0;
bool replaced = false;
@@ -1616,6 +1617,8 @@ static void __msm_console_write(struct uart_port *port, const char *s,
num_newlines++;
count += num_newlines;

+ local_irq_save(flags);
+
if (port->sysrq)
locked = 0;
else if (oops_in_progress)
@@ -1661,6 +1664,8 @@ static void __msm_console_write(struct uart_port *port, const char *s,

if (locked)
spin_unlock(&port->lock);
+
+ local_irq_restore(flags);
}

static void msm_console_write(struct console *co, const char *s,

base-commit: 38a288f5941ef03752887ad86f2d85442358c99a
--
2.30.2

2022-05-10 16:31:05

by Petr Mladek

Subject: Re: [PATCH next v1] serial: msm_serial: disable interrupts in __msm_console_write()

On Fri 2022-05-06 23:39:24, John Ogness wrote:
> __msm_console_write() assumes that interrupts are disabled, but
> with threaded console printers it is possible that the write()
> callback of the console is called with interrupts enabled.

IMHO, it would be nice to include the lockdep splat from
https://lore.kernel.org/r/[email protected]


> Explicitly disable interrupts using local_irq_save() to preserve
> the assumed context.
>
> Reported-by: Marek Szyprowski <[email protected]>
> Signed-off-by: John Ogness <[email protected]>

Otherwise, it looks good to me:

Reviewed-by: Petr Mladek <[email protected]>


> Note: I checked the other serial drivers and this was the only
> one that assumed interrupts off for write().

Great.

Best Regards,
Petr




> drivers/tty/serial/msm_serial.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
> index 23c94b927776..e676ec761f18 100644
> --- a/drivers/tty/serial/msm_serial.c
> +++ b/drivers/tty/serial/msm_serial.c
> @@ -1599,6 +1599,7 @@ static inline struct uart_port *msm_get_port_from_line(unsigned int line)
> static void __msm_console_write(struct uart_port *port, const char *s,
> unsigned int count, bool is_uartdm)
> {
> + unsigned long flags;
> int i;
> int num_newlines = 0;
> bool replaced = false;
> @@ -1616,6 +1617,8 @@ static void __msm_console_write(struct uart_port *port, const char *s,
> num_newlines++;
> count += num_newlines;
>
> + local_irq_save(flags);
> +
> if (port->sysrq)
> locked = 0;
> else if (oops_in_progress)
> @@ -1661,6 +1664,8 @@ static void __msm_console_write(struct uart_port *port, const char *s,
>
> if (locked)
> spin_unlock(&port->lock);
> +
> + local_irq_restore(flags);
> }
>
> static void msm_console_write(struct console *co, const char *s,
>
> base-commit: 38a288f5941ef03752887ad86f2d85442358c99a
> --
> 2.30.2