>
> xilinx_sdfec.c has:
>
> static int xsdfec_dev_open(struct inode *iptr, struct file *fptr)
> {
> return 0;
> }
>
> Which isn't even needed at all, but it is NOT trying to keep people from
> calling open multiple times.
>
> As for why the above logic does not work in your driver, think of what
> happens if someone opens the character device node, and then calls
> dup(2) on it and passes that file descriptor off to another program. Or just
> calls it multiple times from different threads in the same program.
> The kernel does not know what is happening here, and so, "do not allow to
> be opened multiple times" does not do anything to keep userspace from
> actually writing to the device node from multiple processes or threads.
>
> So don't even try, it's not worth it.
>
> > I mean if an application failed at opening the device, how can it
> > proceed to talk the device without a file descriptor?
>
> See above for how to do this.
>
> thanks,
>
> greg k-h
Hi Greg
Thanks for your insight for this. Now I can see this change doesn't prevent
deliberate hacker from opening the driver multiple times.
What I had in mind is that it does prevent some unintentional mistake like some
one accidentally opens the application twice. The second
one would fail due to the change here.
