[PATCH 5.4 050/320] media: dmxdev: fix UAF when dvb_register_device() fails

Greg Kroah-Hartman
2022-01-24T19:52:03Z

From: Wang Hai <wanghai38@huawei.com>

[ Upstream commit ab599eb11882f834951c436cc080c3455ba32b9b ]

I got a use-after-free report:

dvbdev: dvb_register_device: failed to create device dvb1.dvr0 (-12)
...
==================================================================
BUG: KASAN: use-after-free in dvb_dmxdev_release+0xce/0x2f0
...
Call Trace:
dump_stack_lvl+0x6c/0x8b
print_address_description.constprop.0+0x48/0x70
kasan_report.cold+0x82/0xdb
__asan_load4+0x6b/0x90
dvb_dmxdev_release+0xce/0x2f0
...
Allocated by task 7666:
kasan_save_stack+0x23/0x50
__kasan_kmalloc+0x83/0xa0
kmem_cache_alloc_trace+0x22e/0x470
dvb_register_device+0x12f/0x980
dvb_dmxdev_init+0x1f3/0x230
...
Freed by task 7666:
kasan_save_stack+0x23/0x50
kasan_set_track+0x20/0x30
kasan_set_free_info+0x24/0x40
__kasan_slab_free+0xf2/0x130
kfree+0xd1/0x5c0
dvb_register_device.cold+0x1ac/0x1fa
dvb_dmxdev_init+0x1f3/0x230
...

When dvb_register_device() in dvb_dmxdev_init() fails, dvb_dmxdev_init()
does not return a failure, and the memory pointed to by dvbdev or
dvr_dvbdev is invalid at this point. If they are used subsequently, it
will result in UFA or null-ptr-deref.

If dvb_register_device() in dvb_dmxdev_init() fails, fix the bug by making
dvb_dmxdev_init() return an error as well.

Link: https://lore.kernel.org/linux-media/20211015085741.1203283-1-wanghai38@huawei.com

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/dvb-core/dmxdev.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c
index f14a872d12687..e58cb8434dafe 100644
--- a/drivers/media/dvb-core/dmxdev.c
+++ b/drivers/media/dvb-core/dmxdev.c
@@ -1413,7 +1413,7 @@ static const struct dvb_device dvbdev_dvr = {
};
int dvb_dmxdev_init(struct dmxdev *dmxdev, struct dvb_adapter *dvb_adapter)
{
- int i;
+ int i, ret;

if (dmxdev->demux->open(dmxdev->demux) < 0)
return -EUSERS;
@@ -1432,14 +1432,26 @@ int dvb_dmxdev_init(struct dmxdev *dmxdev, struct dvb_adapter *dvb_adapter)
DMXDEV_STATE_FREE);
}

- dvb_register_device(dvb_adapter, &dmxdev->dvbdev, &dvbdev_demux, dmxdev,
+ ret = dvb_register_device(dvb_adapter, &dmxdev->dvbdev, &dvbdev_demux, dmxdev,
DVB_DEVICE_DEMUX, dmxdev->filternum);
- dvb_register_device(dvb_adapter, &dmxdev->dvr_dvbdev, &dvbdev_dvr,
+ if (ret < 0)
+ goto err_register_dvbdev;
+
+ ret = dvb_register_device(dvb_adapter, &dmxdev->dvr_dvbdev, &dvbdev_dvr,
dmxdev, DVB_DEVICE_DVR, dmxdev->filternum);
+ if (ret < 0)
+ goto err_register_dvr_dvbdev;

dvb_ringbuffer_init(&dmxdev->dvr_buffer, NULL, 8192);

return 0;
+
+err_register_dvr_dvbdev:
+ dvb_unregister_device(dmxdev->dvbdev);
+err_register_dvbdev:
+ vfree(dmxdev->filter);
+ dmxdev->filter = NULL;
+ return ret;
}

EXPORT_SYMBOL(dvb_dmxdev_init);
--
2.34.1