From e59eb4adf0d79fe7692c08c07445ec9efc8ddc1c Mon Sep 17 00:00:00 2001
From: Matthias Schwarzott <zzam@gentoo.org>
Date: Wed, 2 Aug 2017 12:46:00 -0400
Subject: [PATCH] media: cx231xx: fix use-after-free when unregistering the
i2c_client for the dvb demod
Calling i2c_unregister_device for a demod driver destroys the frontend object.
Later it is accessed by calling dvb_unregister_frontend and
dvb_frontend_detach.
In some cases this leads to a general protection fault with this
callstack:
dvb_unregister_frontend+0x25/0x50 [dvb_core]
dvb_fini+0xdb/0x160 [cx231xx_dvb]
cx231xx_unregister_extension+0x3d/0xb0 [cx231xx]
cx231xx_dvb_unregister+0x10/0x809 [cx231xx_dvb]
SyS_delete_module+0x18a/0x240
? exit_to_usermode_loop+0x7b/0x80
entry_SYSCALL_64_fastpath+0x17/0x98
Signed-off-by: Matthias Schwarzott <zzam@gentoo.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
---
drivers/media/usb/cx231xx/cx231xx-dvb.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/media/usb/cx231xx/cx231xx-dvb.c b/drivers/media/usb/cx231xx/cx231xx-dvb.c
index ee3eeeb600f8e..c18bb33e060ee 100644
--- a/drivers/media/usb/cx231xx/cx231xx-dvb.c
+++ b/drivers/media/usb/cx231xx/cx231xx-dvb.c
@@ -585,6 +585,9 @@ static void unregister_dvb(struct cx231xx_dvb *dvb)
dvb->demux.dmx.remove_frontend(&dvb->demux.dmx, &dvb->fe_hw);
dvb_dmxdev_release(&dvb->dmxdev);
dvb_dmx_release(&dvb->demux);
+ dvb_unregister_frontend(dvb->frontend);
+ dvb_frontend_detach(dvb->frontend);
+ dvb_unregister_adapter(&dvb->adapter);
/* remove I2C tuner */
client = dvb->i2c_client_tuner;
if (client) {
@@ -597,9 +600,6 @@ static void unregister_dvb(struct cx231xx_dvb *dvb)
module_put(client->dev.driver->owner);
i2c_unregister_device(client);
}
- dvb_unregister_frontend(dvb->frontend);
- dvb_frontend_detach(dvb->frontend);
- dvb_unregister_adapter(&dvb->adapter);
}
static int dvb_init(struct cx231xx *dev)
--
2.39.5