From: Finn Thain <fthain@telegraphics.com.au>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Andy Lutomirski <luto@kernel.org>, Christoph Hellwig <hch@lst.de>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>, David Howells <dhowells@redhat.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
"open list:MIPS" <linux-mips@vger.kernel.org>,
Parisc List <linux-parisc@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-s390 <linux-s390@vger.kernel.org>,
sparclinux <sparclinux@vger.kernel.org>,
linux-block <linux-block@vger.kernel.org>,
Linux SCSI List <linux-scsi@vger.kernel.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
linux-aio <linux-aio@kvack.org>,
io-uring@vger.kernel.org, linux-arch <linux-arch@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Network Development <netdev@vger.kernel.org>,
keyrings@vger.kernel.org,
LSM List <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag
Date: Sun, 20 Sep 2020 07:52:38 +1000 (AEST) [thread overview]
Message-ID: <alpine.LNX.2.23.453.2009200745310.6@nippy.intranet> (raw)
In-Reply-To: <CAK8P3a2Mi+1yttyGk4k7HxRVrMtmFqJewouVhynqUL0PJycmog@mail.gmail.com>
On Sat, 19 Sep 2020, Arnd Bergmann wrote:
> On Sat, Sep 19, 2020 at 6:21 PM Andy Lutomirski <luto@kernel.org> wrote:
> > On Fri, Sep 18, 2020 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
> > > On Fri, Sep 18, 2020 at 02:58:22PM +0100, Al Viro wrote:
> > > > Said that, why not provide a variant that would take an explicit
> > > > "is it compat" argument and use it there? And have the normal one
> > > > pass in_compat_syscall() to that...
> > >
> > > That would help to not introduce a regression with this series yes.
> > > But it wouldn't fix existing bugs when io_uring is used to access
> > > read or write methods that use in_compat_syscall(). One example
> > > that I recently ran into is drivers/scsi/sg.c.
>
> Ah, so reading /dev/input/event* would suffer from the same issue, and
> that one would in fact be broken by your patch in the hypothetical case
> that someone tried to use io_uring to read /dev/input/event on x32...
>
> For reference, I checked the socket timestamp handling that has a number
> of corner cases with time32/time64 formats in compat mode, but none of
> those appear to be affected by the problem.
>
> > Aside from the potentially nasty use of per-task variables, one thing
> > I don't like about PF_FORCE_COMPAT is that it's one-way. If we're
> > going to have a generic mechanism for this, shouldn't we allow a full
> > override of the syscall arch instead of just allowing forcing compat
> > so that a compat syscall can do a non-compat operation?
>
> The only reason it's needed here is that the caller is in a kernel
> thread rather than a system call. Are there any possible scenarios where
> one would actually need the opposite?
>
Quite possibly. The ext4 vs. compat getdents bug is still unresolved.
Please see,
https://lore.kernel.org/lkml/CAFEAcA9W+JK7_TrtTnL1P2ES1knNPJX9wcUvhfLwxLq9augq1w@mail.gmail.com/
> Arnd
>
next prev parent reply other threads:[~2020-09-19 22:03 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.LNX.2.23.453.2009200745310.6@nippy.intranet \
--to=fthain@telegraphics.com.au \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=axboe@kernel.dk \
--cc=dhowells@redhat.com \
--cc=hch@lst.de \
--cc=io-uring@vger.kernel.org \
--cc=keyrings@vger.kernel.org \
--cc=linux-aio@kvack.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-parisc@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=luto@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=peter.maydell@linaro.org \
--cc=sparclinux@vger.kernel.org \
--cc=viro@zeniv.linux.org.uk \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).