linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Nicolas Boichat <drinkcat@chromium.org>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	Ian Lance Taylor <iant@google.com>,
	Luis Lozano <llozano@chromium.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Dave Chinner <david@fromorbit.com>,
	linux-fsdevel@vger.kernel.org,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/6] vfs: Disallow copy_file_range on generated file systems
Date: Fri, 12 Feb 2021 13:24:51 +0800	[thread overview]
Message-ID: <CANMq1KDBiPN3mE4vQ=DJc-YirPm_OP9wDfeacuKZHMLhhEYj+w@mail.gmail.com> (raw)
In-Reply-To: <20210212045902.GG7187@magnolia>

On Fri, Feb 12, 2021 at 12:59 PM Darrick J. Wong <djwong@kernel.org> wrote:
>
> On Thu, Feb 11, 2021 at 08:53:47PM -0800, Darrick J. Wong wrote:
> > On Fri, Feb 12, 2021 at 12:44:05PM +0800, Nicolas Boichat wrote:
> > > copy_file_range (which calls generic_copy_file_checks) uses the
> > > inode file size to adjust the copy count parameter. This breaks
> > > with special filesystems like procfs/sysfs/debugfs/tracefs, where
> > > the file size appears to be zero, but content is actually returned
> > > when a read operation is performed. Other issues would also
> > > happen on partial writes, as the function would attempt to seek
> > > in the input file.
> > >
> > > Use the newly introduced FS_GENERATED_CONTENT filesystem flag
> > > to return -EOPNOTSUPP: applications can then retry with a more
> > > usual read/write based file copy (the fallback code is usually
> > > already present to handle older kernels).
> > >
> > > Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
> > > ---
> > >
> > >  fs/read_write.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/fs/read_write.c b/fs/read_write.c
> > > index 0029ff2b0ca8..80322e89fb0a 100644
> > > --- a/fs/read_write.c
> > > +++ b/fs/read_write.c
> > > @@ -1485,6 +1485,9 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
> > >     if (flags != 0)
> > >             return -EINVAL;
> > >
> > > +   if (file_inode(file_in)->i_sb->s_type->fs_flags & FS_GENERATED_CONTENT)
> > > +           return -EOPNOTSUPP;
> >
> > Why not declare a dummy copy_file_range_nop function that returns
> > EOPNOTSUPP and point all of these filesystems at it?
> >
> > (Or, I guess in these days where function pointers are the enemy,
> > create a #define that is a cast of 0x1, and fix do_copy_file_range to
> > return EOPNOTSUPP if it sees that?)

I was pondering abusing ERR_PTR(-EOPNOTSUPP) for this purpose ,-P

>
> Oh, I see, because that doesn't help if the source file is procfs and
> the dest file is (say) xfs, because the generic version will try to do
> splice magic and *poof*.

Yep. I mean, we could still add a check if the
file_in->f_op->copy_file_range == copy_file_range_nop in
do_copy_file_range...
But then we'd need to sprinkle .copy_file_range = copy_file_range_nop
in many many places (~700 as a lower bound[1]), since the file
operation structure is defined at the file level, not at the FS level,
and people are likely to forget...

[1]
$ git grep "struct file_operations.*=" | grep debug | wc -l
631
$ git grep "struct file_operations.*=" | grep trace | wc -l
84

>
> I guess the other nit thatI can think of at this late hour is ... what
> about the other virtual filesystems like configfs and whatnot?  Should
> we have a way to flag them as "this can't be the source of a CFR
> request" as well?
>
> Or is it just trace/debug/proc/sysfs that have these "zero size but
> readable" speshul behaviors?

I did try to audit the other filesystems. The ones I spotted:
 - devpts should be fine (only device nodes in there)
 - I think pstore doesn't need the flag as it's RAM-backed and persistent.

But yes, I missed configfs, thanks for catching that. I think we need
to add the flag for that one (looks like the sizes are all 4K).

>
> --D
>
> >
> > --D
> >
> > > +
> > >     ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len,
> > >                                    flags);
> > >     if (unlikely(ret))
> > > --
> > > 2.30.0.478.g8a0d178c01-goog
> > >

  reply	other threads:[~2021-02-12  5:25 UTC|newest]

Thread overview: 136+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-12  4:43 [PATCH 0/6] Add generated flag to filesystem struct to block copy_file_range Nicolas Boichat
2021-02-12  4:44 ` [PATCH 1/6] fs: Add flag to file_system_type to indicate content is generated Nicolas Boichat
2021-02-12  7:46   ` Greg KH
2021-02-12  8:20     ` Nicolas Boichat
2021-02-12  8:37       ` Greg KH
2021-02-12 15:33         ` Ian Lance Taylor
2021-02-12 15:45           ` Greg KH
2021-02-12 15:59             ` Ian Lance Taylor
2021-02-12 16:28               ` Greg KH
2021-02-12 20:22                 ` Ian Lance Taylor
2021-02-12 23:03             ` Dave Chinner
2021-02-12 23:07               ` Ian Lance Taylor
2021-02-12 23:27                 ` Dave Chinner
2021-02-12 23:54                   ` Darrick J. Wong
2021-02-15  0:38                     ` Dave Chinner
2021-02-15  1:12                       ` Ian Lance Taylor
2021-02-15  1:25                         ` Nicolas Boichat
2021-02-15  5:56                           ` Amir Goldstein
2021-02-15  8:30                           ` Greg KH
2021-02-12  8:22     ` Amir Goldstein
2021-02-12  8:39       ` Greg KH
2021-02-12 12:05         ` Luis Henriques
2021-02-12 12:18           ` Greg KH
2021-02-12 12:41             ` Luis Henriques
2021-02-12 14:11               ` Greg KH
2021-02-12 15:01                 ` Luis Henriques
2021-02-15  6:12               ` Amir Goldstein
2021-02-15 10:39                 ` Luis Henriques
2021-02-15 12:22                   ` Luis Henriques
2021-02-15 14:23                     ` Amir Goldstein
2021-02-15 14:51                       ` Luis Henriques
2021-02-15 15:43                       ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Luis Henriques
2021-02-15 16:02                         ` Trond Myklebust
2021-02-16  0:25                           ` Steve French
2021-02-15 16:34                         ` Amir Goldstein
2021-02-15 16:53                           ` Trond Myklebust
2021-02-15 17:24                             ` Amir Goldstein
2021-02-15 18:57                               ` Trond Myklebust
2021-02-15 19:43                                 ` Amir Goldstein
2021-02-16 11:17                                   ` Luis Henriques
2021-02-16 11:28                                     ` gregkh
2021-02-16 12:01                                       ` Luis Henriques
2021-02-16 12:08                                         ` Greg KH
2021-02-16 13:51                                     ` Amir Goldstein
2021-02-16 16:42                                       ` Luis Henriques
2021-02-16 17:44                                         ` Amir Goldstein
2021-02-16 18:55                                           ` Luis Henriques
2021-02-16 19:20                                             ` Amir Goldstein
2021-02-16 19:27                                               ` Anna Schumaker
2021-02-16 19:31                                                 ` Steve French
2021-02-16 19:40                                                   ` Amir Goldstein
2021-02-16 21:15                                                     ` Steve French
2021-02-17  8:08                                                       ` Amir Goldstein
2021-02-17 17:26                                                         ` [PATCH v3] vfs: fix copy_file_range regression in cross-fs copies Luis Henriques
2021-02-17 20:47                                                           ` Amir Goldstein
2021-02-18  0:56                                                           ` Nicolas Boichat
2021-02-18  5:32                                                           ` Olga Kornievskaia
2021-02-18  6:47                                                             ` Amir Goldstein
2021-02-18 16:28                                                               ` Olga Kornievskaia
2021-02-18  7:43                                                           ` Christoph Hellwig
2021-02-18  0:50                                                         ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Andreas Dilger
2021-02-18  7:34                                                           ` gregkh
2021-02-16 18:54                                       ` Andreas Dilger
2021-02-17  4:45                         ` Nicolas Boichat
2021-02-18  7:42                         ` Christoph Hellwig
2021-02-18  9:10                           ` Amir Goldstein
2021-02-18 10:29                             ` Luis Henriques
2021-02-18 12:15                               ` Luis Henriques
2021-02-18 12:49                                 ` Amir Goldstein
2021-02-18 14:36                                   ` [PATCH v4] vfs: fix copy_file_range regression in cross-fs copies Luis Henriques
2021-02-18 14:58                                     ` Amir Goldstein
2021-02-18 15:17                                       ` [PATCH v5] " Luis Henriques
2021-02-18 15:53                                         ` Amir Goldstein
2021-02-18 16:35                                           ` Luis Henriques
2021-02-18 17:18                                             ` [PATCH v6] " Luis Henriques
2021-02-19 21:18                                               ` Olga Kornievskaia
2021-02-19 21:52                                                 ` Amir Goldstein
2021-02-21 19:58                                                 ` [PATCH v7] " Luis Henriques
2021-02-22  3:00                                                   ` Nicolas Boichat
2021-02-22 10:24                                                   ` [PATCH v8] " Luis Henriques
2021-02-22 10:46                                                     ` Amir Goldstein
2021-02-22 16:25                                                     ` dai.ngo
2021-02-23 10:32                                                       ` Luis Henriques
2021-02-23 15:28                                                         ` Amir Goldstein
2021-02-23 15:29                                                         ` dai.ngo
2021-02-23 16:02                                                           ` dai.ngo
2021-02-23 16:47                                                             ` Amir Goldstein
2021-02-23 16:57                                                               ` dai.ngo
     [not found]                                                                 ` <e3eed18b-fc7e-e687-608b-7f662017329c@oracle.com>
2021-02-23 17:33                                                                   ` Amir Goldstein
2021-02-24  0:13                                                                     ` dai.ngo
2021-02-23 17:56                                                                 ` Luis Henriques
2021-02-23 17:13                                                             ` Olga Kornievskaia
2021-02-24  1:00                                                     ` Olga Kornievskaia
2021-02-24 10:23                                                       ` Luis Henriques
2021-02-24 10:44                                                         ` Nicolas Boichat
2021-04-09  5:23                                                           ` Nicolas Boichat
2021-04-09 13:39                                                             ` Luis Henriques
2021-04-09 13:50                                                               ` Amir Goldstein
2021-04-23  4:40                                                                 ` Nicolas Boichat
2021-05-03  8:54                                                                   ` Luis Henriques
2021-05-10  4:59                                                                     ` Amir Goldstein
2021-05-10  9:10                                                                       ` Luis Henriques
2021-02-24 14:23                                                     ` [PATCH] copy_file_range.2: Kernel v5.12 updates Luis Henriques
2021-02-24 16:10                                                       ` Amir Goldstein
2021-02-25 10:21                                                         ` Luis Henriques
2021-02-26 10:13                                                           ` Alejandro Colomar (man-pages)
2021-02-26 10:34                                                             ` Amir Goldstein
2021-02-26 11:15                                                               ` Alejandro Colomar (man-pages)
2021-02-26 13:59                                                                 ` Jeff Layton
2021-02-26 21:26                                                                   ` Alejandro Colomar (man-pages)
2021-02-26 22:18                                                         ` Alejandro Colomar (man-pages)
2021-02-27  5:41                                                           ` Amir Goldstein
2021-02-27 12:20                                                             ` Alejandro Colomar (man-pages)
2021-02-27 13:49                                                               ` [RFC v2] copy_file_range.2: Update cross-filesystem support for 5.12 Alejandro Colomar
2021-02-27 16:00                                                                 ` Amir Goldstein
2021-02-27 23:08                                                             ` [PATCH] copy_file_range.2: Kernel v5.12 updates Steve French
2021-02-28  7:35                                                               ` Amir Goldstein
2021-02-28 22:25                                                                 ` Steve French
2021-03-01  6:18                                                                   ` Amir Goldstein
2021-03-01 14:41                                                       ` [RFC v3] copy_file_range.2: Update cross-filesystem support for 5.12 Alejandro Colomar
2021-03-01 14:58                                                         ` Amir Goldstein
2021-03-04  9:38                                                       ` [RFC v4] " Alejandro Colomar
2021-03-04 17:13                                                         ` Darrick J. Wong
2021-03-04 18:24                                                           ` Alejandro Colomar (man-pages)
2021-03-04 23:50                                                             ` Darrick J. Wong
2021-02-24  7:15                                     ` [PATCH v4] vfs: fix copy_file_range regression in cross-fs copies Amir Goldstein
2021-02-24  8:30                                       ` Petr Vorel
2021-02-18 20:41                             ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Steve French
2021-02-12 23:15       ` [PATCH 1/6] fs: Add flag to file_system_type to indicate content is generated Dave Chinner
2021-02-12  7:54   ` Amir Goldstein
2021-02-12  4:44 ` [PATCH 2/6] proc: Add FS_GENERATED_CONTENT to filesystem flags Nicolas Boichat
2021-02-12  4:44 ` [PATCH 6/6] vfs: Disallow copy_file_range on generated file systems Nicolas Boichat
2021-02-12  4:53   ` Darrick J. Wong
2021-02-12  4:59     ` Darrick J. Wong
2021-02-12  5:24       ` Nicolas Boichat [this message]
2021-02-14 23:09 ` [PATCH 0/6] Add generated flag to filesystem struct to block copy_file_range Al Viro

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='CANMq1KDBiPN3mE4vQ=DJc-YirPm_OP9wDfeacuKZHMLhhEYj+w@mail.gmail.com' \
    --to=drinkcat@chromium.org \
    --cc=david@fromorbit.com \
    --cc=djwong@kernel.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=iant@google.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=llozano@chromium.org \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: [PATCH 6/6] vfs: Disallow copy_file_range on generated file systems' \
    /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

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).