Commits
Max Kellermann committed f17c403af9b
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>