Re: [RFC PATCH 2/3] fs: add RWF_ENCODED for writing compressed data

[Colin Walters]

On Wed, Sep 25, 2019, at 3:11 AM, Dave Chinner wrote:
>
> We're talking about user data read/write access here, not some
> special security capability. Access to the data has already been
> permission checked, so why should the format that the data is
> supplied to the kernel in suddenly require new privilege checks?

What happens with BTRFS today if userspace provides invalid compressed data via 
this interface?  Does that show up as filesystem corruption later?  If the data 
is verified at write time, wouldn't that be losing most of the speed advantages 
of providing pre-compressed data?

Ability for a user to cause fsck errors later would be a new thing that would 
argue for a privilege check I think.