[PATCH 4.19 03/48] vt: fix unicode console freeing with a common interface

Greg Kroah-Hartman
2020-05-13T09:46:22Z

From: Nicolas Pitre <nico@fluxnic.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@fluxnic.net>
Reported-by: syzbot+0bfda3ade1ee9288a1be@syzkaller.appspotmail.com
Fixes: 9a98e7a80f95 ("vt: don't use kmalloc() for the unicode screen buffer")
Cc: <stable@vger.kernel.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://lore.kernel.org/r/nycvar.YSQ.7.76.2005021043110.2671@knanqh.ubzr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.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 ca8c6ddc1ca8c..5c7a968a5ea67 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;
}

@@ -1233,7 +1238,7 @@ 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