On Wed, 17 Apr 2013, Benjamin Tissoires wrote:
> If an event occurs while the hid debugfs is forwarding events, list->tail
> is updated during copy_to_user().
>
> Remove the gotos and use a regular while-loop to empty the queue.
>
> Second benefit, it checks that we are not writing more than count bytes
> to the user-space output buffer.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
> ---
> drivers/hid/hid-debug.c | 27 +++++++++++----------------
> 1 file changed, 11 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
> index 094cbcf..1dc8104 100644
> --- a/drivers/hid/hid-debug.c
> +++ b/drivers/hid/hid-debug.c
> @@ -1000,6 +1000,7 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
> size_t count, loff_t *ppos)
> {
> struct hid_debug_list *list = file->private_data;
> + char *buf_head;
> int ret = 0, len;
> DECLARE_WAITQUEUE(wait, current);
>
> @@ -1039,28 +1040,22 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
> goto out;
>
> /* pass the ringbuffer contents to userspace */
> -copy_rest:
> - if (list->tail == list->head)
> - goto out;
> - if (list->tail > list->head) {
> - len = list->tail - list->head;
> + while (list->tail != list->head && ret < count) {
> + buf_head = &list->hid_debug_buf[list->head];
>
> - if (copy_to_user(buffer + ret, &list->hid_debug_buf[list->head], len)) {
> - ret = -EFAULT;
> - goto out;
> - }
> - ret += len;
> - list->head += len;
> - } else {
> - len = HID_DEBUG_BUFSIZE - list->head;
> + if (list->tail > list->head)
> + len = list->tail - list->head;
> + else
> + len = HID_DEBUG_BUFSIZE - list->head;
> +
> + len = min(count - ret, len);
This triggers a type checking warning in min(), and it seems to be correct
on this one (mixing size_t with signed int).
drivers/hid/hid-debug.c:1079: warning: comparison of distinct pointer types lacks a cast
--
Jiri Kosina
SUSE Labs
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