linux-ext4 - Re: [PATCH 2/2] fsverity: move sysctl registration out of signature.c

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Date:   Wed, 6 Sep 2023 21:12:09 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Joel Granados <j.granados@...sung.com>
Cc:     fsverity@...ts.linux.dev, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, linux-btrfs@...r.kernel.org
Subject: Re: [PATCH 2/2] fsverity: move sysctl registration out of signature.c

On Wed, Sep 06, 2023 at 03:49:04PM +0200, Joel Granados wrote:
> On Wed, Jul 05, 2023 at 02:27:43PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@...gle.com>
> > 
> > Currently the registration of the fsverity sysctls happens in
> > signature.c, which couples it to CONFIG_FS_VERITY_BUILTIN_SIGNATURES.
> > 
> > This makes it hard to add new sysctls unrelated to builtin signatures.
> > 
> > Also, some users have started checking whether the directory
> > /proc/sys/fs/verity exists as a way to tell whether fsverity is
> > supported.  This isn't the intended method; instead, the existence of
> > /sys/fs/$fstype/features/verity should be checked, or users should just
> > try to use the fsverity ioctls.  Regardlesss, it should be made to work
> > as expected without a dependency on CONFIG_FS_VERITY_BUILTIN_SIGNATURES.
> > 
> > Therefore, move the sysctl registration into init.c.  With
> > CONFIG_FS_VERITY_BUILTIN_SIGNATURES, nothing changes.  Without it, but
> > with CONFIG_FS_VERITY, an empty list of sysctls is now registered.
> > 
> > Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> > ---
> >  fs/verity/fsverity_private.h |  1 +
> >  fs/verity/init.c             | 32 ++++++++++++++++++++++++++++++++
> >  fs/verity/signature.c        | 33 +--------------------------------
> >  3 files changed, 34 insertions(+), 32 deletions(-)
> > 
> > diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h
> > index c5ab9023dd2d3..d071a6e32581e 100644
> > --- a/fs/verity/fsverity_private.h
> > +++ b/fs/verity/fsverity_private.h
> > @@ -123,6 +123,7 @@ void __init fsverity_init_info_cache(void);
> >  /* signature.c */
> >  
> >  #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
> > +extern int fsverity_require_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 bcd11d63eb1ca..a29f062f6047b 100644
> > --- a/fs/verity/init.c
> > +++ b/fs/verity/init.c
> > @@ -9,6 +9,37 @@
> >  
> >  #include <linux/ratelimit.h>
> >  
> > +#ifdef CONFIG_SYSCTL
> > +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,
> > +		.maxlen         = sizeof(int),
> > +		.mode           = 0644,
> > +		.proc_handler   = proc_dointvec_minmax,
> > +		.extra1         = SYSCTL_ZERO,
> > +		.extra2         = SYSCTL_ONE,
> > +	},
> > +#endif
> > +	{ }
> > +};
> > +
> Just to double check: When CONFIG_FS_VERITY_BUILTIN_SIGNATURES is not
> defined then you expect an empty directory under "fs/verity". right?

Yes, that's correct.

- Eric