Re: [PATCH 0/3] SG_IO command filtering via sysfs

[Christoph Hellwig]

On Fri, Nov 16, 2018 at 10:45:11AM +0100, Paolo Bonzini wrote:
> Yeah, but looking at the command is what Ted wants.  The thing that we
> did in RHEL was a single sysfs bool that allows unfiltered access,
> because it was sort of enough and made the delta very small.  But for
> upstream I want to do it right, even if that means learning all that
> new-fangled BPF stuff. :)

So what is this magic command?

> I would even agree, however it's allowed right now and I would be
> surprised if no one was relying on it in good faith ("I'm just doing an
> INQUIRY, why do I need to open O_RDWR").  And indeed:
> 
> $ sudo chmod a+r /dev/sda
> $ strace -e openat sg_inq /dev/sda
> openat(AT_FDCWD, "/dev/sda", O_RDONLY|O_NONBLOCK) = 3

Well, not if we only did that for unprivileged opens.