From: Arnd Bergmann <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: Andy Lutomirski <[email protected]>, Christoph Hellwig <[email protected]>,
Al Viro <[email protected]>,
Andrew Morton <[email protected]>,
Jens Axboe <[email protected]>, David Howells <[email protected]>,
linux-arm-kernel <[email protected]>,
X86 ML <[email protected]>, LKML <[email protected]>,
"open list:MIPS" <[email protected]>,
Parisc List <[email protected]>,
linuxppc-dev <[email protected]>,
linux-s390 <[email protected]>,
sparclinux <[email protected]>,
linux-block <[email protected]>,
Linux SCSI List <[email protected]>,
Linux FS Devel <[email protected]>,
linux-aio <[email protected]>,
[email protected], linux-arch <[email protected]>,
Linux-MM <[email protected]>,
Network Development <[email protected]>,
[email protected],
LSM List <[email protected]>
Subject: Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
Date: Tue, 22 Sep 2020 11:01:32 +0200 [thread overview]
Message-ID: <CAK8P3a39jN+t2hhLg0oKZnbYATQXmYE2-Z1JkmFyc1EPdg1HXw@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
On Tue, Sep 22, 2020 at 9:59 AM Pavel Begunkov <[email protected]> wrote:
> On 22/09/2020 10:23, Arnd Bergmann wrote:
> > On Tue, Sep 22, 2020 at 8:32 AM Pavel Begunkov <[email protected]> wrote:
> >> On 22/09/2020 03:58, Andy Lutomirski wrote:
> >>> On Mon, Sep 21, 2020 at 5:24 PM Pavel Begunkov <[email protected]> wrote:
> >>> I may be looking at a different kernel than you, but aren't you
> >>> preventing creating an io_uring regardless of whether SQPOLL is
> >>> requested?
> >>
> >> I diffed a not-saved file on a sleepy head, thanks for noticing.
> >> As you said, there should be an SQPOLL check.
> >>
> >> ...
> >> if (ctx->compat && (p->flags & IORING_SETUP_SQPOLL))
> >> goto err;
> >
> > Wouldn't that mean that now 32-bit containers behave differently
> > between compat and native execution?
> >
> > I think if you want to prevent 32-bit applications from using SQPOLL,
> > it needs to be done the same way on both to be consistent:
>
> The intention was to disable only compat not native 32-bit.
I'm not following why that would be considered a valid option,
as that clearly breaks existing users that update from a 32-bit
kernel to a 64-bit one.
Taking away the features from users that are still on 32-bit kernels
already seems questionable to me, but being inconsistent
about it seems much worse, in particular when the regression
is on the upgrade path.
> > Can we expect all existing and future user space to have a sane
> > fallback when IORING_SETUP_SQPOLL fails?
>
> SQPOLL has a few differences with non-SQPOLL modes, but it's easy
> to convert between them. Anyway, SQPOLL is a privileged special
> case that's here for performance/latency reasons, I don't think
> there will be any non-accidental users of it.
Ok, so the behavior of 32-bit tasks would be the same as running
the same application as unprivileged 64-bit tasks, with applications
already having to implement that fallback, right?
Arnd
next prev parent reply other threads:[~2020-09-22 9:01 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-18 12:45 let import_iovec deal with compat_iovecs as well Christoph Hellwig
2020-09-18 12:45 ` [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag Christoph Hellwig
2020-09-18 13:40 ` Al Viro
2020-09-18 13:44 ` Christoph Hellwig
2020-09-18 13:58 ` Al Viro
2020-09-18 15:16 ` Christoph Hellwig
2020-09-19 16:21 ` Andy Lutomirski
2020-09-19 21:16 ` Arnd Bergmann
2020-09-19 21:52 ` Finn Thain
2020-09-19 22:22 ` Andy Lutomirski
2020-09-21 16:10 ` Pavel Begunkov
2020-09-21 16:13 ` Pavel Begunkov
2020-09-21 23:51 ` Andy Lutomirski
2020-09-22 0:22 ` Pavel Begunkov
2020-09-22 0:58 ` Andy Lutomirski
2020-09-22 6:30 ` Pavel Begunkov
2020-09-22 7:23 ` Arnd Bergmann
2020-09-22 7:57 ` Pavel Begunkov
2020-09-22 9:01 ` Arnd Bergmann [this message]
2020-09-22 16:20 ` Andy Lutomirski
2020-09-23 8:01 ` Pavel Begunkov
2020-09-23 13:22 ` Al Viro
2020-09-19 22:09 ` Al Viro
2020-09-19 22:23 ` Andy Lutomirski
2020-09-19 22:41 ` Al Viro
2020-09-19 22:53 ` Andy Lutomirski
2020-09-19 23:24 ` Al Viro
2020-09-20 0:14 ` Andy Lutomirski
2020-09-20 2:57 ` Al Viro
2020-09-20 16:59 ` Andy Lutomirski
2020-09-20 18:12 ` Al Viro
2020-09-20 13:55 ` Arnd Bergmann
2020-09-20 15:02 ` Al Viro
2020-09-19 14:53 ` David Laight
2020-09-18 13:59 ` Arnd Bergmann
2020-09-20 15:15 ` Matthew Wilcox
2020-09-20 15:55 ` William Kucharski
2020-09-21 16:20 ` Pavel Begunkov
2020-09-20 16:00 ` Arnd Bergmann
2020-09-20 18:07 ` Al Viro
2020-09-20 18:41 ` Al Viro
2020-09-20 19:01 ` Matthew Wilcox
2020-09-20 19:10 ` Al Viro
2020-09-20 19:22 ` Matthew Wilcox
2020-09-20 19:28 ` Andy Lutomirski
2020-09-20 20:49 ` Arnd Bergmann
2020-09-20 21:13 ` David Laight
2020-09-21 16:31 ` Pavel Begunkov
2020-09-20 21:42 ` Al Viro
2020-09-21 16:26 ` Pavel Begunkov
2020-09-20 19:14 ` Andy Lutomirski
2020-09-21 4:28 ` Christoph Hellwig
2020-09-18 12:45 ` [PATCH 2/9] compat.h: fix a spelling error in <linux/compat.h> Christoph Hellwig
2020-09-18 13:37 ` Johannes Thumshirn
2020-09-18 12:45 ` [PATCH 3/9] fs: explicitly check for CHECK_IOVEC_ONLY in rw_copy_check_uvector Christoph Hellwig
2020-09-18 12:56 ` Matthew Wilcox
2020-09-18 13:39 ` Johannes Thumshirn
2020-09-18 12:45 ` [PATCH 4/9] fs: handle the compat case in import_iovec Christoph Hellwig
2020-09-18 12:45 ` [PATCH 5/9] fs: remove various compat readv/writev helpers Christoph Hellwig
2020-09-18 12:45 ` [PATCH 6/9] fs: remove the compat readv/writev syscalls Christoph Hellwig
2020-09-18 12:45 ` [PATCH 7/9] fs: remove compat_sys_vmsplice Christoph Hellwig
2020-09-18 12:45 ` [PATCH 8/9] mm: remove compat_process_vm_{readv,writev} Christoph Hellwig
2020-09-18 13:48 ` Arnd Bergmann
2020-09-18 12:45 ` [PATCH 9/9] security/keys: remove compat_keyctl_instantiate_key_iov Christoph Hellwig
2020-09-19 14:24 ` let import_iovec deal with compat_iovecs as well David Laight
2020-09-21 4:41 ` 'Christoph Hellwig'
2020-09-21 11:11 ` David Laight
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