diff options
| author | David Lechner <david@lechnology.com> | 2021-10-17 13:55:21 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-10-19 11:36:28 +0200 |
| commit | f5245a5fdf757f50a6c905fc16cceb1a6146ccf5 (patch) | |
| tree | 80a651b5444b70ceff26f93d2e97e37cd64c6f7b /drivers/counter | |
| parent | c3ed761c9e1e4987406671b326dab48a048614ee (diff) | |
| download | lwn-f5245a5fdf757f50a6c905fc16cceb1a6146ccf5.tar.gz lwn-f5245a5fdf757f50a6c905fc16cceb1a6146ccf5.zip | |
counter: drop chrdev_lock
This removes the chrdev_lock from the counter subsystem. This was
intended to prevent opening the chrdev more than once. However, this
doesn't work in practice since userspace can duplicate file descriptors
and pass file descriptors to other processes. Since this protection
can't be relied on, it is best to just remove it.
Suggested-by: Greg KH <gregkh@linuxfoundation.org>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: David Lechner <david@lechnology.com>
Link: https://lore.kernel.org/r/20211017185521.3468640-1-david@lechnology.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/counter')
| -rw-r--r-- | drivers/counter/counter-chrdev.c | 6 | ||||
| -rw-r--r-- | drivers/counter/counter-sysfs.c | 13 |
2 files changed, 3 insertions, 16 deletions
diff --git a/drivers/counter/counter-chrdev.c b/drivers/counter/counter-chrdev.c index 967c94ae95bb..b747dc81cfc6 100644 --- a/drivers/counter/counter-chrdev.c +++ b/drivers/counter/counter-chrdev.c @@ -384,10 +384,6 @@ static int counter_chrdev_open(struct inode *inode, struct file *filp) typeof(*counter), chrdev); - /* Ensure chrdev is not opened more than 1 at a time */ - if (!atomic_add_unless(&counter->chrdev_lock, 1, 1)) - return -EBUSY; - get_device(&counter->dev); filp->private_data = counter; @@ -419,7 +415,6 @@ out_unlock: mutex_unlock(&counter->ops_exist_lock); put_device(&counter->dev); - atomic_dec(&counter->chrdev_lock); return ret; } @@ -445,7 +440,6 @@ int counter_chrdev_add(struct counter_device *const counter) mutex_init(&counter->events_lock); /* Initialize character device */ - atomic_set(&counter->chrdev_lock, 0); cdev_init(&counter->chrdev, &counter_fops); /* Allocate Counter events queue */ diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c index c2fddbb0d442..8c2d7c29ea59 100644 --- a/drivers/counter/counter-sysfs.c +++ b/drivers/counter/counter-sysfs.c @@ -796,25 +796,18 @@ static int counter_events_queue_size_write(struct counter_device *counter, u64 val) { DECLARE_KFIFO_PTR(events, struct counter_event); - int err = 0; - - /* Ensure chrdev is not opened more than 1 at a time */ - if (!atomic_add_unless(&counter->chrdev_lock, 1, 1)) - return -EBUSY; + int err; /* Allocate new events queue */ err = kfifo_alloc(&events, val, GFP_KERNEL); if (err) - goto exit_early; + return err; /* Swap in new events queue */ kfifo_free(&counter->events); counter->events.kfifo = events.kfifo; -exit_early: - atomic_dec(&counter->chrdev_lock); - - return err; + return 0; } static struct counter_comp counter_num_signals_comp = |