linux-kernel - Re: [PATCH 2/4] aio: Remove the now superfluous sentinel elements from ctl

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Date:   Thu, 9 Nov 2023 17:00:40 +0100
From:   Joel Granados <j.granados@...sung.com>
To:     Eric Biggers <ebiggers@...nel.org>
CC:     Luis Chamberlain <mcgrof@...nel.org>, <willy@...radead.org>,
        <josh@...htriplett.org>, Kees Cook <keescook@...omium.org>,
        David Howells <dhowells@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Benjamin LaHaise <bcrl@...ck.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>, Neil Brown <neilb@...e.de>,
        Olga Kornievskaia <kolga@...app.com>,
        Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
        Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
        Matthew Bobrowski <repnop@...gle.com>,
        Anton Altaparmakov <anton@...era.com>,
        Namjae Jeon <linkinjeon@...nel.org>,
        Mark Fasheh <mark@...heh.com>,
        Joel Becker <jlbec@...lplan.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Iurii Zaikin <yzaikin@...gle.com>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Chandan Babu R <chandan.babu@...cle.com>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Jan Harkes <jaharkes@...cmu.edu>, <coda@...cmu.edu>,
        <linux-cachefs@...hat.com>, <linux-kernel@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>, <linux-aio@...ck.org>,
        <linux-mm@...ck.org>, <linux-nfs@...r.kernel.org>,
        <linux-ntfs-dev@...ts.sourceforge.net>,
        <ocfs2-devel@...ts.linux.dev>, <fsverity@...ts.linux.dev>,
        <linux-xfs@...r.kernel.org>, <codalist@...emann.coda.cs.cmu.edu>
Subject: Re: [PATCH 2/4] aio: Remove the now superfluous sentinel elements
 from ctl_table array

On Tue, Nov 07, 2023 at 07:42:31PM -0800, Eric Biggers wrote:
> On Tue, Nov 07, 2023 at 02:44:21PM +0100, Joel Granados via B4 Relay wrote:
> > [PATCH 2/4] aio: Remove the now superfluous sentinel elements from ctl_table array
> 
> The commit prefix should be "fs:".
> 
> > Remove sentinel elements ctl_table struct. Special attention was placed in
> > making sure that an empty directory for fs/verity was created when
> > CONFIG_FS_VERITY_BUILTIN_SIGNATURES is not defined. In this case we use the
> > register sysctl call that expects a size.
> [...]
> > diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
> > index d071a6e32581..8191bf7ad706 100644
> > --- a/fs/verity/fsverity_private.h
> > +++ b/fs/verity/fsverity_private.h
> > @@ -122,8 +122,8 @@ void __init fsverity_init_info_cache(void);
> >  
> >  /* signature.c */
> >  
> > -#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> >  extern int fsverity_require_signatures;
> > +#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> >  int fsverity_verify_signature(const struct fsverity_info *vi,
> >  			      const u8 *signature, size_t sig_size);
> >  
> > diff --git a/fs/verity/init.c b/fs/verity/init.c
> > index a29f062f6047..e31045dd4f6c 100644
> > --- a/fs/verity/init.c
> > +++ b/fs/verity/init.c
> > @@ -13,7 +13,6 @@
> >  static struct ctl_table_header *fsverity_sysctl_header;
> >  
> >  static struct ctl_table fsverity_sysctl_table[] = {
> > -#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> >  	{
> >  		.procname       = "require_signatures",
> >  		.data           = &fsverity_require_signatures,
> > @@ -23,14 +22,17 @@ static struct ctl_table fsverity_sysctl_table[] = {
> >  		.extra1         = SYSCTL_ZERO,
> >  		.extra2         = SYSCTL_ONE,
> >  	},
> > -#endif
> > -	{ }
> >  };
> >  
> >  static void __init fsverity_init_sysctl(void)
> >  {
> > +#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> >  	fsverity_sysctl_header = register_sysctl("fs/verity",
> >  						 fsverity_sysctl_table);
> > +#else
> > +	fsverity_sysctl_header = register_sysctl_sz("fs/verity",
> > +						 fsverity_sysctl_table, 0);
> > +#endif
> >  	if (!fsverity_sysctl_header)
> >  		panic("fsverity sysctl registration failed");
> 
> This does not make sense, and it causes a build error when CONFIG_FS_VERITY=y
> and CONFIG_FS_VERITY_BUILTIN_SIGNATURES=n.
> 
> I think all you need to do is delete the sentinel element, the same as
> everywhere else.  I just tested it, and it works fine.
I found the reason why I added the CONFIG_FS_VERITY_BUILTIN_SIGNATURES
here: it is related to
https://lore.kernel.org/all/20230705212743.42180-3-ebiggers@kernel.org/
where the directory is registered with an element only if
CONFIG_FS_VERITY_BUILTIN_SIGNATURES is defined. I had forgotten, but I
even asked for a clarification on the patch :).

I see that that patch made it to v6.6. So the solution is not to remove
the CONFIG_FS_VERITY_BUILTIN_SIGNATURES, but for me to rebase on top of
a more up to date base.

@Eric: Please get back to me if the patch in
https://lore.kernel.org/all/20230705212743.42180-3-ebiggers@kernel.org/
is no longer relevant.

Best.

> 
> BTW, the comments for register_sysctl_sz() and __register_sysctl_table() are
> outdated, as they still say "A completely 0 filled entry terminates the table."
> 
> - Eric

-- 

Joel Granados

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