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From: Pavel Begunkov <[email protected]>
To: Arnd Bergmann <[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 10:57:11 +0300	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAK8P3a2-6JNS38EbZcLrk=cTT526oP=Rf0aoqWNSJ-k4XTYehQ@mail.gmail.com>

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.

> 
>    if ((!IS_ENABLED(CONFIG_64BIT) || ctx->compat) &&
>         (p->flags & IORING_SETUP_SQPOLL))
>             goto err;
> 
> I don't really see how taking away SQPOLL from 32-bit tasks is
> any better than just preventing access to the known-broken files
> as Al suggested, or adding the hack to make it work as in
> Christoph's original patch.

That's why I'm hoping that Christoph's work and the discussion will
reach consensus, but the bug should be patched in the end. IMHO,
it's a good and easy enough fallback option (temporal?).

> 
> 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.
-- 
Pavel Begunkov

  reply	other threads:[~2020-09-22  7:59 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 [this message]
2020-09-22  9:01                                 ` Arnd Bergmann
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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