2020-05-02 15:03:15

by Nicolas Pitre

Subject: [PATCH] vt: fix unicode console freeing with a common interface

By directly using kfree() in different places we risk missing one if
it is switched to using vfree(), especially if the corresponding
vmalloc() is hidden away within a common abstraction.

Oh wait, that's exactly what happened here.

So let's fix this by creating a common abstraction for the free case
as well.

Signed-off-by: Nicolas Pitre <[email protected]>
Reported-by: [email protected]
Fixes: 9a98e7a80f95 ("vt: don't use kmalloc() for the unicode screen buffer")
Cc: <[email protected]>

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index e5ffed795e..48a8199f78 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -365,9 +365,14 @@ static struct uni_screen *vc_uniscr_alloc(unsigned int cols, unsigned int rows)
return uniscr;
}

+static void vc_uniscr_free(struct uni_screen *uniscr)
+{
+ vfree(uniscr);
+}
+
static void vc_uniscr_set(struct vc_data *vc, struct uni_screen *new_uniscr)
{
- vfree(vc->vc_uni_screen);
+ vc_uniscr_free(vc->vc_uni_screen);
vc->vc_uni_screen = new_uniscr;
}

@@ -1230,7 +1235,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
err = resize_screen(vc, new_cols, new_rows, user);
if (err) {
kfree(newscreen);
- kfree(new_uniscr);
+ vc_uniscr_free(new_uniscr);
return err;
}

2020-05-02 15:59:48

by Sam Ravnborg

Subject: Re: [PATCH] vt: fix unicode console freeing with a common interface

Hi Nicolas

On Sat, May 02, 2020 at 11:01:07AM -0400, Nicolas Pitre wrote:
> By directly using kfree() in different places we risk missing one if
> it is switched to using vfree(), especially if the corresponding
> vmalloc() is hidden away within a common abstraction.
>
> Oh wait, that's exactly what happened here.
>
> So let's fix this by creating a common abstraction for the free case
> as well.
>
> Signed-off-by: Nicolas Pitre <[email protected]>
> Reported-by: [email protected]
> Fixes: 9a98e7a80f95 ("vt: don't use kmalloc() for the unicode screen buffer")
> Cc: <[email protected]>

Looks good.
Reviewed-by: Sam Ravnborg <[email protected]>

Not the I know the code, but verified that no more kfree() was
used for vc_uni_screen.

Sam

>
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index e5ffed795e..48a8199f78 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -365,9 +365,14 @@ static struct uni_screen *vc_uniscr_alloc(unsigned int cols, unsigned int rows)
> return uniscr;
> }
>
> +static void vc_uniscr_free(struct uni_screen *uniscr)
> +{
> + vfree(uniscr);
> +}
> +
> static void vc_uniscr_set(struct vc_data *vc, struct uni_screen *new_uniscr)
> {
> - vfree(vc->vc_uni_screen);
> + vc_uniscr_free(vc->vc_uni_screen);
> vc->vc_uni_screen = new_uniscr;
> }
>
> @@ -1230,7 +1235,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
> err = resize_screen(vc, new_cols, new_rows, user);
> if (err) {
> kfree(newscreen);
> - kfree(new_uniscr);
> + vc_uniscr_free(new_uniscr);
> return err;
> }
>