Re: [PATCH] cgroup/misc: Fix an overflow

[Haitao Huang]

On Mon, 17 Jul 2023 13:57:59 -0500, Tejun Heo <tj@xxxxxxxxxx> wrote:

> On Mon, Jul 17, 2023 at 06:55:32PM +0000, Jarkko Sakkinen wrote:
> > On Mon Jul 17, 2023 at 6:47 PM UTC, Haitao Huang wrote:
> > > The variable 'new_usage' in misc_cg_try_charge() may overflow if it
> > > becomes above INT_MAX. This was observed when I implement the new SGX
> > > EPC cgroup[1] as a misc cgroup and test on a platform with large SGX  
> > EPC
> > > sizes.
> > >
> > > Change type of new_usage to long from int and check overflow.
> > >
> > > Fixes: a72232eabdfcf ("cgroup: Add misc cgroup controller")
> > > Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
> > >
> > > [1]  
> > https://lore.kernel.org/linux-sgx/20230712230202.47929-1-haitao.huang@xxxxxxxxxxxxxxx/
> > > ---
> > >  kernel/cgroup/misc.c | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
> > > index fe3e8a0eb7ed..ff9f900981a3 100644
> > > --- a/kernel/cgroup/misc.c
> > > +++ b/kernel/cgroup/misc.c
> > > @@ -143,7 +143,7 @@ int misc_cg_try_charge(enum misc_res_type type,  
> > struct misc_cg *cg,
> > >  	struct misc_cg *i, *j;
> > >  	int ret;
> > >  	struct misc_res *res;
> > > -	int new_usage;
> > > +	long new_usage;
> > >
> > >  	if (!(valid_type(type) && cg && READ_ONCE(misc_res_capacity[type])))
> > >  		return -EINVAL;
> > > @@ -153,10 +153,10 @@ int misc_cg_try_charge(enum misc_res_type type,  
> > struct misc_cg *cg,
> > >
> > >  	for (i = cg; i; i = parent_misc(i)) {
> > >  		res = &i->res[type];
> > > -
> >
> > This is extra noise in the patch, please remove the change.
>
> Lemme just revert it. Haitao, can you instead make the resource counters  
> and
> all related variables explicit 64bit instead?

Will do.
Thanks
Haitao