From 2ab25d35a91098ef0f42d478cc37f6a5591a4ab0 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Tue, 2 Aug 2016 08:13:57 -0300 Subject: [PATCH] [media] cec: improve locking - The global lock was used in cec_get_device when it should have used the devnode lock. - cec_put_device also took the global lock, but since the release function takes that lock as well this could lead to a deadlock. Just don't take the lock here since there is no reason for it. - cec_devnode_register() should take the global lock when clearing the bit in the global bitmap. - In cec_devnode_unregister() place the devnode->(un)register tests and assignments under the devnode lock as well: this has to be in a critical block. Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- drivers/staging/media/cec/cec-core.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/drivers/staging/media/cec/cec-core.c b/drivers/staging/media/cec/cec-core.c index 73792d078462..3b1e4d2b190d 100644 --- a/drivers/staging/media/cec/cec-core.c +++ b/drivers/staging/media/cec/cec-core.c @@ -51,31 +51,29 @@ int cec_get_device(struct cec_devnode *devnode) { /* * Check if the cec device is available. This needs to be done with - * the cec_devnode_lock held to prevent an open/unregister race: + * the devnode->lock held to prevent an open/unregister race: * without the lock, the device could be unregistered and freed between * the devnode->registered check and get_device() calls, leading to * a crash. */ - mutex_lock(&cec_devnode_lock); + mutex_lock(&devnode->lock); /* * return ENXIO if the cec device has been removed * already or if it is not registered anymore. */ if (!devnode->registered) { - mutex_unlock(&cec_devnode_lock); + mutex_unlock(&devnode->lock); return -ENXIO; } /* and increase the device refcount */ get_device(&devnode->dev); - mutex_unlock(&cec_devnode_lock); + mutex_unlock(&devnode->lock); return 0; } void cec_put_device(struct cec_devnode *devnode) { - mutex_lock(&cec_devnode_lock); put_device(&devnode->dev); - mutex_unlock(&cec_devnode_lock); } /* Called when the last user of the cec device exits. */ @@ -84,11 +82,10 @@ static void cec_devnode_release(struct device *cd) struct cec_devnode *devnode = to_cec_devnode(cd); mutex_lock(&cec_devnode_lock); - /* Mark device node number as free */ clear_bit(devnode->minor, cec_devnode_nums); - mutex_unlock(&cec_devnode_lock); + cec_delete_adapter(to_cec_adapter(devnode)); } @@ -160,7 +157,9 @@ static int __must_check cec_devnode_register(struct cec_devnode *devnode, cdev_del: cdev_del(&devnode->cdev); clr_bit: + mutex_lock(&cec_devnode_lock); clear_bit(devnode->minor, cec_devnode_nums); + mutex_unlock(&cec_devnode_lock); return ret; } @@ -177,17 +176,21 @@ static void cec_devnode_unregister(struct cec_devnode *devnode) { struct cec_fh *fh; + mutex_lock(&devnode->lock); + /* Check if devnode was never registered or already unregistered */ - if (!devnode->registered || devnode->unregistered) + if (!devnode->registered || devnode->unregistered) { + mutex_unlock(&devnode->lock); return; + } - mutex_lock(&devnode->lock); list_for_each_entry(fh, &devnode->fhs, list) wake_up_interruptible(&fh->wait); - mutex_unlock(&devnode->lock); devnode->registered = false; devnode->unregistered = true; + mutex_unlock(&devnode->lock); + device_del(&devnode->dev); cdev_del(&devnode->cdev); put_device(&devnode->dev); -- 2.34.1