Re: [PATCH v3 2/2] sysctl: Fix underflow value setting risk in vm_table

[Nicolas Bouchinet]

Hi Joel,

Thank's for your reply.

On 1/15/25 11:27, Joel Granados wrote:
> On Tue, Dec 17, 2024 at 02:29:07PM +0100, nicolas.bouchinet@xxxxxxxxxxx wrote:
> > From: Nicolas Bouchinet <nicolas.bouchinet@xxxxxxxxxxx>
> >
> > Commit 3b3376f222e3 ("sysctl.c: fix underflow value setting risk in vm_table")
> > fixes underflow value setting risk in vm_table but misses vdso_enabled
> > sysctl.
> >
> > vdso_enabled sysctl is initialized with .extra1 value as SYSCTL_ZERO to
> > avoid negative value writes but the proc_handler is proc_dointvec and
> > not proc_dointvec_minmax and thus do not uses .extra1 and .extra2.
> >
> > The following command thus works :
> >
> > `# echo -1 > /proc/sys/vm/vdso_enabled`
> >
> > This patch properly sets the proc_handler to proc_dointvec_minmax.
> Please also mention that you added a extra* arg.
ACK, will push soon.
> > Fixes: 3b3376f222e3 ("sysctl.c: fix underflow value setting risk in vm_table")
> > Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@xxxxxxxxxxx>
> > ---
> >   kernel/sysctl.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index 79e6cb1d5c48f..6d8a4fceb79aa 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -2194,8 +2194,9 @@ static struct ctl_table vm_table[] = {
> >   		.maxlen		= sizeof(vdso_enabled),
> >   #endif
> >   		.mode		= 0644,
> > -		.proc_handler	= proc_dointvec,
> > +		.proc_handler	= proc_dointvec_minmax,
> >   		.extra1		= SYSCTL_ZERO,
> > +		.extra1		= SYSCTL_ONE,
> * What did you mean here?
>    1. To replace extra1 with SYSCTL_ONE?
>    2. To add extra2 as SYSCTL_ONE and you mistyped it as "extra1"?
Oh, my bad, it's indeed a mistype, extra1 should be set at SYSCTL_ZERO, 
extra2 to SYSCTL_ONE.
It seems you already corrected it in [3]. LGTM, thank's.
> * This patch conflicts with the vm_table moving out of the kernel
>    directory [1] from Kaixiong Yu <yukaixiong@xxxxxxxxxx> (which is also
>    in sysctl-testing). I have fixed this conflict with [2], please scream
>    if you see that messed up.
>
> * Please send an updated version addressing these comments and taking
>    into account that your patches will go after [1]. You can use [3] as
>    your base if you prefer.


Thank's for the links, I'll reword the commit message on [3] since you 
already fixed the typo
and that [1] is already applied.

> Best
>
>
> [1] https://lore.kernel.org/20250111070751.2588654-14-yukaixiong@xxxxxxxxxx
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl.git/commit/?h=sysctl-testing&id=81b34e7966e84983a31c0150cbf2171605c023a3
> [3] https://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl.git/commit/?h=sysctl-testing&id=2fc99f285719e0cce8df1fe21479cb9e6626c2fe

Best regards,

Nicolas