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authorMax Kellermann2018-05-03 14:12:59 -0400
committerMauro Carvalho Chehab2018-05-11 12:09:59 -0400
commitf17c403af9bf3dc19069cb8c10390030ee4c8fb0 (patch)
treee9cb56c8eda3e1b02348386dd345bc030fa64162 /drivers/media/usb
parent2a5f2705c97625aa1a4e1dd4d584eaa05392e060 (diff)
media: dvbdev: add a mutex protecting the "mdev" pointer
During destruction, a race condition in dvb_media_controller_disable_source() can cause a kernel crash, because the "mdev" pointer has been read successfully while another task executes dvb_usb_media_device_unregister(), which destroys the object. Example for such a crash: general protection fault: 0000 [#1] SMP CPU: 1 PID: 301 Comm: vdr Not tainted 4.8.1-nuc+ #102 [142B blob data] task: ffff8802301f2040 task.stack: ffff880233728000 RIP: 0010:[<ffffffff816c296b>] [<ffffffff816c296b>] dvb_frontend_release+0xcb/0x120 RSP: 0018:ffff88023372bdd8 EFLAGS: 00010202 RAX: 001fd55c000000da RBX: ffff880236bad810 RCX: 0000000000000000 RDX: ffff880235bd81f0 RSI: 0000000000000246 RDI: ffff880235bd81e8 RBP: ffff88023372be00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: ffff88022f009910 R12: 0000000000000000 R13: ffff880235a21a80 R14: ffff880235bd8000 R15: ffff880235bb8a78 FS: 0000000000000000(0000) GS:ffff88023fd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f96edd69818 CR3: 0000000002406000 CR4: 00000000001006e0 Stack: ffff88022f009900 0000000000000008 ffff880235bb8a78 ffff8802344fbb20 ffff880236437b40 ffff88023372be48 ffffffff8117a81e ffff880235bb8a78 ffff88022f009910 ffff8802335a7400 ffff8802301f2040 ffff88022f009900 Call Trace: [<ffffffff8117a81e>] __fput+0xde/0x1d0 [<ffffffff8117a949>] ____fput+0x9/0x10 [<ffffffff810a9fce>] task_work_run+0x7e/0xa0 [<ffffffff81094bab>] do_exit+0x27b/0xa50 [<ffffffff810407e3>] ? __do_page_fault+0x1c3/0x430 [<ffffffff81095402>] do_group_exit+0x42/0xb0 [<ffffffff8109547f>] SyS_exit_group+0xf/0x10 [<ffffffff8108bedb>] entry_SYSCALL_64_fastpath+0x13/0x8f Code: 31 c9 49 8d be e8 01 00 00 ba 01 00 00 00 be 03 00 00 00 e8 68 2d a0 ff 48 8b 83 10 03 00 00 48 8b 80 88 00 00 00 48 85 c0 74 12 <48> 8b 80 88 02 00 00 48 85 c0 74 06 49 8b 7d RIP [<ffffffff816c296b>] dvb_frontend_release+0xcb/0x120 [mchehab+samsung@kernel.org: fix a Coding Style issue] Signed-off-by: Max Kellermann <max.kellermann@gmail.com> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Diffstat (limited to 'drivers/media/usb')
-rw-r--r--drivers/media/usb/dvb-usb/dvb-usb-dvb.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/media/usb/dvb-usb/dvb-usb-dvb.c b/drivers/media/usb/dvb-usb/dvb-usb-dvb.c
index 3a66e732e0d8..8056053c9ab0 100644
--- a/drivers/media/usb/dvb-usb/dvb-usb-dvb.c
+++ b/drivers/media/usb/dvb-usb/dvb-usb-dvb.c
@@ -132,10 +132,14 @@ static void dvb_usb_media_device_unregister(struct dvb_usb_adapter *adap)
if (!adap->dvb_adap.mdev)
return;
+ mutex_lock(&adap->dvb_adap.mdev_lock);
+
media_device_unregister(adap->dvb_adap.mdev);
media_device_cleanup(adap->dvb_adap.mdev);
kfree(adap->dvb_adap.mdev);
adap->dvb_adap.mdev = NULL;
+
+ mutex_unlock(&adap->dvb_adap.mdev_lock);
#endif
}