Re: [PATCH v2 2/6] sysctl: Fixes nsm_local_state bounds

[Joel Granados]

On Mon, Feb 24, 2025 at 09:38:17AM -0500, Chuck Lever wrote:
> On 2/24/25 4:58 AM, nicolas.bouchinet@xxxxxxxxxxx wrote:
> > From: Nicolas Bouchinet <nicolas.bouchinet@xxxxxxxxxxx>
> > 
> > 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@xxxxxxxxxxx>
> > ---
> >  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@xxxxxxxxxx>

Best

> 
> 
> -- 
> Chuck Lever

-- 

Joel Granados