Hi Peter,
On Thu, Jan 27, 2011 at 12:21:30PM +0100, Peter Korsgaard wrote:
> >>>>> "Henrik" == Henrik Rydberg <rydberg@xxxxxxxxxxx> writes:
> >> @@ -321,6 +321,9 @@ static ssize_t evdev_write(struct file *file, const
> >> char __user *buffer,
> >> struct input_event event;
> >> int retval;
> >>
> >> + if (count < input_event_size())
> >> + return -EINVAL;
> >> +
>
> Henrik> This assumes that write will only ever be called with sufficient
> Henrik> data. It is not an error to write (and report) less data than
> Henrik> specified, so perhaps the above will yield unpleasant surprises.
>
> Well, like this it's consistent with evdev_read(). We can only consume
> complete input_event structures, so we can either return 0 (no events
> consumed) or -EINVAL (invalid data).
>
> Before the patch we returned sizeof input_event (if data after write
> buffer is accessible) or -EINVAL otherwise.
>
> The v1 patch returned 0, but that causes problems with userspace, as it
> often does:
>
> wlile (len) {
> n = write(fd, buf, len);
> if (n <= 0) break;
> len -= n;
> buf += n;
> }
>
> Which will then loop forever.
Well this code won't loop forever, since n == 0. Only if you do:
if (n < 0) break;
That is.
baruch
> Returning -EINVAL on something that can never work seems like the sanest
> option.
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