From f17c403af9bf3dc19069cb8c10390030ee4c8fb0 Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Thu, 3 May 2018 14:12:59 -0400 Subject: 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:[] [] 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: [] __fput+0xde/0x1d0 [] ____fput+0x9/0x10 [] task_work_run+0x7e/0xa0 [] do_exit+0x27b/0xa50 [] ? __do_page_fault+0x1c3/0x430 [] do_group_exit+0x42/0xb0 [] SyS_exit_group+0xf/0x10 [] 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 [] dvb_frontend_release+0xcb/0x120 [mchehab+samsung@kernel.org: fix a Coding Style issue] Signed-off-by: Max Kellermann Signed-off-by: Mauro Carvalho Chehab --- drivers/media/dvb-core/dvb_frontend.c | 7 +++++++ drivers/media/dvb-core/dvbdev.c | 4 ++++ 2 files changed, 11 insertions(+) (limited to 'drivers/media/dvb-core') diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c index bc5eaad0f915..f64141662a82 100644 --- a/drivers/media/dvb-core/dvb_frontend.c +++ b/drivers/media/dvb-core/dvb_frontend.c @@ -2732,6 +2732,7 @@ static int dvb_frontend_open(struct inode *inode, struct file *file) fepriv->voltage = -1; #ifdef CONFIG_MEDIA_CONTROLLER_DVB + mutex_lock(&fe->dvb->mdev_lock); if (fe->dvb->mdev) { mutex_lock(&fe->dvb->mdev->graph_mutex); if (fe->dvb->mdev->enable_source) @@ -2740,11 +2741,13 @@ static int dvb_frontend_open(struct inode *inode, struct file *file) &fepriv->pipe); mutex_unlock(&fe->dvb->mdev->graph_mutex); if (ret) { + mutex_unlock(&fe->dvb->mdev_lock); dev_err(fe->dvb->device, "Tuner is busy. Error %d\n", ret); goto err2; } } + mutex_unlock(&fe->dvb->mdev_lock); #endif ret = dvb_frontend_start (fe); if (ret) @@ -2762,12 +2765,14 @@ static int dvb_frontend_open(struct inode *inode, struct file *file) err3: #ifdef CONFIG_MEDIA_CONTROLLER_DVB + mutex_lock(&fe->dvb->mdev_lock); if (fe->dvb->mdev) { mutex_lock(&fe->dvb->mdev->graph_mutex); if (fe->dvb->mdev->disable_source) fe->dvb->mdev->disable_source(dvbdev->entity); mutex_unlock(&fe->dvb->mdev->graph_mutex); } + mutex_unlock(&fe->dvb->mdev_lock); err2: #endif dvb_generic_release(inode, file); @@ -2799,12 +2804,14 @@ static int dvb_frontend_release(struct inode *inode, struct file *file) if (dvbdev->users == -1) { wake_up(&fepriv->wait_queue); #ifdef CONFIG_MEDIA_CONTROLLER_DVB + mutex_lock(&fe->dvb->mdev_lock); if (fe->dvb->mdev) { mutex_lock(&fe->dvb->mdev->graph_mutex); if (fe->dvb->mdev->disable_source) fe->dvb->mdev->disable_source(dvbdev->entity); mutex_unlock(&fe->dvb->mdev->graph_mutex); } + mutex_unlock(&fe->dvb->mdev_lock); #endif if (fe->exit != DVB_FE_NO_EXIT) wake_up(&dvbdev->wait_queue); diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c index 787fe06df217..64d6793674b9 100644 --- a/drivers/media/dvb-core/dvbdev.c +++ b/drivers/media/dvb-core/dvbdev.c @@ -859,6 +859,10 @@ int dvb_register_adapter(struct dvb_adapter *adap, const char *name, adap->mfe_dvbdev = NULL; mutex_init (&adap->mfe_lock); +#ifdef CONFIG_MEDIA_CONTROLLER_DVB + mutex_init(&adap->mdev_lock); +#endif + list_add_tail (&adap->list_head, &dvb_adapter_list); mutex_unlock(&dvbdev_register_lock); -- cgit v1.2.3