linux-kernel - [PATCH 5.4 08/90] vt: fix unicode console freeing with a common interface

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Message-Id: <20200513094409.974392275@linuxfoundation.org>
Date:   Wed, 13 May 2020 11:44:04 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nicolas Pitre <nico@...xnic.net>,
        syzbot+0bfda3ade1ee9288a1be@...kaller.appspotmail.com,
        Sam Ravnborg <sam@...nborg.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 08/90] vt: fix unicode console freeing with a common interface

From: Nicolas Pitre <nico@...xnic.net>

[ Upstream commit 57d38f26d81e4275748b69372f31df545dcd9b71 ]

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>
Reviewed-by: Sam Ravnborg <sam@...nborg.org>
Link: https://lore.kernel.org/r/nycvar.YSQ.7.76.2005021043110.2671@knanqh.ubzr
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/vt/vt.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 8b3ecef50394a..fd0361d72738b 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;
 	}
 
-- 
2.20.1