linux-kernel - Re: [PATCH v2 2/6] sysctl: Fixes nsm_local

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Message-ID: <42t2lpwwwihg4heu4ogudt4fe5uz7trg3y2lsoqvmjnzmhnjmy@pebnborzqodv>
Date: Mon, 3 Mar 2025 15:12:57 +0100
From: Joel Granados <joel.granados@...nel.org>
To: Chuck Lever <chuck.lever@...cle.com>
Cc: nicolas.bouchinet@...p-os.org, linux-kernel@...r.kernel.org, 
	linux-rdma@...r.kernel.org, linux-scsi@...r.kernel.org, codalist@...a.cs.cmu.edu, 
	linux-nfs@...r.kernel.org, Nicolas Bouchinet <nicolas.bouchinet@....gouv.fr>, 
	Joel Granados <j.granados@...sung.com>, Clemens Ladisch <clemens@...isch.de>, 
	Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>, 
	"James E.J. Bottomley" <James.Bottomley@...senpartnership.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	Jan Harkes <jaharkes@...cmu.edu>, Jeff Layton <jlayton@...nel.org>, Neil Brown <neilb@...e.de>, 
	Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>, 
	Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>, 
	Bart Van Assche <bvanassche@....org>, Zhu Yanjun <yanjun.zhu@...ux.dev>, 
	Al Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH v2 2/6] sysctl: Fixes nsm_local_state bounds

On Mon, Feb 24, 2025 at 09:38:17AM -0500, Chuck Lever wrote:
> On 2/24/25 4:58 AM, nicolas.bouchinet@...p-os.org wrote:
> > From: Nicolas Bouchinet <nicolas.bouchinet@....gouv.fr>
> > 
> > Bound nsm_local_state sysctl writings between SYSCTL_ZERO
> > and SYSCTL_INT_MAX.
> > 
> > The proc_handler has thus been updated to proc_dointvec_minmax.
> > 
> > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@....gouv.fr>
> > ---
> >  fs/lockd/svc.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
> > index 2c8eedc6c2cc9..984ab233af8b6 100644
> > --- a/fs/lockd/svc.c
> > +++ b/fs/lockd/svc.c
> > @@ -461,7 +461,9 @@ static const struct ctl_table nlm_sysctls[] = {
> >  		.data		= &nsm_local_state,
> >  		.maxlen		= sizeof(int),
> >  		.mode		= 0644,
> > -		.proc_handler	= proc_dointvec,
> > +		.proc_handler	= proc_dointvec_minmax,
> > +		.extra1		= SYSCTL_ZERO,
> > +		.extra2		= SYSCTL_INT_MAX,
> >  	},
> >  };
> >  
> 
> Hi Nicolas -
> 
> nsm_local_state is an unsigned 32-bit integer. The type of that value is
> defined by spec, because this value is exchanged between peers on the
> network.
> 
> Perhaps this patch should replace proc_dointvec with proc_douintvec
> instead.
As Nicolas stated, that is completely up to how you used the variable.

Things to notice:
1. If you want the full range of a unsigned long, then you should stop
   using proc_dointvec as it will upper limit the value to INT_MAX.
2. If you want to keep using nsm_local_state as unsigned int, then
   please add SYSCTL_ZERO as a lower bound to avoid assigning negative
   values
3. Having SYSCTL_INT_MAX is not necessary as it is already capped by
   proc_dointvec{_minmax,}, but it is nice to have as it makes explicit
   what is happening.

Let me know if you take this through your trees so I can remove it from
sysctl.

Reviewed-by: Joel Granados <joel.granados@...nel.org>

Best

> 
> 
> -- 
> Chuck Lever

-- 

Joel Granados