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media: cx231xx: fix use-after-free when unregistering the i2c_client for the dvb demod

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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>
This commit is contained in:
Matthias Schwarzott 2017-08-02 12:46:00 -04:00 committed by Mauro Carvalho Chehab
parent 412b16d623
commit e59eb4adf0
1 changed files with 3 additions and 3 deletions
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6
drivers/media/usb/cx231xx/cx231xx-dvb.c
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@ -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)