linux-kernel - Re: [PATCH 1/9] kernel: add a PF_FORCE

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Message-ID: <20200920214229.GR3421308@ZenIV.linux.org.uk>
Date:   Sun, 20 Sep 2020 22:42:29 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>, Arnd Bergmann <arnd@...db.de>,
        David Howells <dhowells@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-block@...r.kernel.org, linux-scsi@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
        io-uring@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, netdev@...r.kernel.org,
        keyrings@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag

On Sun, Sep 20, 2020 at 08:22:59PM +0100, Matthew Wilcox wrote:
> On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
> > IMO it's much saner to mark those and refuse to touch them from io_uring...
> 
> Simpler solution is to remove io_uring from the 32-bit syscall list.
> If you're a 32-bit process, you don't get to use io_uring.  Would
> any real users actually care about that?

What for?  I mean, is there any reason to try and keep those bugs as
first-class citizens?  IDGI...  Yes, we have several special files
(out of thousands) that have read()/write() user-visible semantics
broken wrt 32bit/64bit.  And we have to keep them working that way
for existing syscalls.  Why would we want to pretend that their
behaviour is normal and isn't an ABI bug, not to be repeated for
anything new?