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

Joel Granados
2025-03-03T14:13:02Z

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

Best

>
>
> --
> Chuck Lever

--

Joel Granados