linux-kernel - [PATCH] vt: fix unicode console freeing with a common interface

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Date:   Sat, 2 May 2020 11:01:07 -0400 (EDT)
From:   Nicolas Pitre <nico@...xnic.net>
To:     gregkh@...uxfoundation.org
cc:     jslaby@...e.com, daniel.vetter@...ll.ch, sam@...nborg.org,
        linux-kernel@...r.kernel.org
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 <nico@...xnic.net>
Reported-by: syzbot+0bfda3ade1ee9288a1be@...kaller.appspotmail.com
Fixes: 9a98e7a80f95 ("vt: don't use kmalloc() for the unicode screen buffer")
Cc: <stable@...r.kernel.org>

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;
 	}