Since commit 3579b59c7edc475013ae769a2d26d99733c95f13 ("printk: refactor
and rework printing logic"), con->write is called without checking if it
is implemented in the console driver. This does make some sense, because
for all "normal" consoles it is vital to have a write function.
As the ttynull console driver does not need any console output the write
function was not implemented. This caused a "unable to handle kernel NULL
pointer dereference" when the write function is called now.
To fix this issue, implement an empty write function.
Signed-off-by: Michael Thalmeier <[email protected]>
Cc: [email protected]
---
drivers/tty/ttynull.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/tty/ttynull.c b/drivers/tty/ttynull.c
index 1d4438472442..6e9323544a7d 100644
--- a/drivers/tty/ttynull.c
+++ b/drivers/tty/ttynull.c
@@ -40,6 +40,12 @@ static unsigned int ttynull_write_room(struct tty_struct *tty)
return 65536;
}
+
+static void ttynull_console_write(struct console *co, const char *buf,
+ unsigned count)
+{
+}
+
static const struct tty_operations ttynull_ops = {
.open = ttynull_open,
.close = ttynull_close,
@@ -56,6 +62,7 @@ static struct tty_driver *ttynull_device(struct console *c, int *index)
static struct console ttynull_console = {
.name = "ttynull",
+ .write = ttynull_console_write,
.device = ttynull_device,
};
--
2.39.1
On Tue, Feb 14, 2023 at 11:23:17AM +0100, Michael Thalmeier wrote:
> Since commit 3579b59c7edc475013ae769a2d26d99733c95f13 ("printk: refactor
Nit, sha ids should only be 12 digits, as per the kernel documentation,
can you fix that up?
And wait, that's not even a commit id, are you sure that is correct?
> and rework printing logic"), con->write is called without checking if it
> is implemented in the console driver. This does make some sense, because
> for all "normal" consoles it is vital to have a write function.
> As the ttynull console driver does not need any console output the write
> function was not implemented. This caused a "unable to handle kernel NULL
> pointer dereference" when the write function is called now.
>
> To fix this issue, implement an empty write function.
>
> Signed-off-by: Michael Thalmeier <[email protected]>
> Cc: [email protected]
Adding a Fixes: tag here would also be good to have.
thanks,
greg k-h