From: David Laight <David.Laight@ACULAB.COM>
To: 'Arnd Bergmann' <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>,
Al Viro <viro@zeniv.linux.org.uk>, Christoph Hellwig <hch@lst.de>,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>, David Howells <dhowells@redhat.com>,
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"open list:MIPS" <linux-mips@vger.kernel.org>,
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Subject: RE: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
Date: Sun, 20 Sep 2020 21:13:24 +0000 [thread overview]
Message-ID: <8363d874e503470f8caa201e85e9fbd4@AcuMS.aculab.com> (raw)
In-Reply-To: <CAK8P3a37BRFj_qg61gP2oVrjJzBrZ58y1vggeTk_5n55Ou5U2Q@mail.gmail.com>
From: Arnd Bergmann
> Sent: 20 September 2020 21:49
>
> On Sun, Sep 20, 2020 at 9:28 PM Andy Lutomirski <luto@kernel.org> wrote:
> > On Sun, Sep 20, 2020 at 12:23 PM Matthew Wilcox <willy@infradead.org> 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?
> >
> > We could go one step farther and declare that we're done adding *any*
> > new compat syscalls :)
>
> Would you also stop adding system calls to native 32-bit systems then?
>
> On memory constrained systems (less than 2GB a.t.m.), there is still a
> strong demand for running 32-bit user space, but all of the recent Arm
> cores (after Cortex-A55) dropped the ability to run 32-bit kernels, so
> that compat mode may eventually become the primary way to run
> Linux on cheap embedded systems.
>
> I don't think there is any chance we can realistically take away io_uring
> from the 32-bit ABI any more now.
Can't it just run requests from 32bit apps in a kernel thread that has
the 'in_compat_syscall' flag set?
Not that i recall seeing the code where it saves the 'compat' nature
of any requests.
It is already completely f*cked if you try to pass the command ring
to a child process - it uses the wrong 'mm'.
I suspect there are some really horrid security holes in that area.
David.
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-09-20 21:13 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
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 [this message]
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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