media: dvb-core: Fix use-after-free due to race at dvb_register_device()
authorHyunwoo Kim <imv4bel@gmail.com>
Thu, 17 Nov 2022 04:59:24 +0000 (04:59 +0000)
committerMauro Carvalho Chehab <mchehab@kernel.org>
Sun, 14 May 2023 05:30:58 +0000 (06:30 +0100)
commit627bb528b086b4136315c25d6a447a98ea9448d3
tree47b999d037e43720c4cf1bfed135c88f118e393f
parent4172385b0c9ac366dcab78eda48c26814b87ed1a
media: dvb-core: Fix use-after-free due to race at dvb_register_device()

dvb_register_device() dynamically allocates fops with kmemdup()
to set the fops->owner.
And these fops are registered in 'file->f_ops' using replace_fops()
in the dvb_device_open() process, and kfree()d in dvb_free_device().

However, it is not common to use dynamically allocated fops instead
of 'static const' fops as an argument of replace_fops(),
and UAF may occur.
These UAFs can occur on any dvb type using dvb_register_device(),
such as dvb_dvr, dvb_demux, dvb_frontend, dvb_net, etc.

So, instead of kfree() the fops dynamically allocated in
dvb_register_device() in dvb_free_device() called during the
.disconnect() process, kfree() it collectively in exit_dvbdev()
called when the dvbdev.c module is removed.

Link: https://lore.kernel.org/linux-media/20221117045925.14297-4-imv4bel@gmail.com
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
drivers/media/dvb-core/dvbdev.c
include/media/dvbdev.h