Re: [PATCH 0/3] Fix some seq_file users that were recently broken

[Jakub Kicinski]

On Fri, 5 Feb 2021 14:35:50 -0800 Andrew Morton wrote:
> On Fri, 05 Feb 2021 11:36:30 +1100 NeilBrown <neilb@xxxxxxx> wrote:
> 
> > A recent change to seq_file broke some users which were using seq_file
> > in a non-"standard" way ...  though the "standard" isn't documented, so
> > they can be excused.  The result is a possible leak - of memory in one
> > case, of references to a 'transport' in the other.
> > 
> > These three patches:
> >  1/ document and explain the problem
> >  2/ fix the problem user in x86
> >  3/ fix the problem user in net/sctp
> 
> 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and
> interface") was August 2018, so I don't think "recent" applies here?
> 
> I didn't look closely, but it appears that the sctp procfs file is
> world-readable.  So we gave unprivileged userspace the ability to leak
> kernel memory?
> 
> So I'm thinking that we aim for 5.12-rc1 on all three patches with a cc:stable?

I'd rather take the sctp patch sooner, we'll send another batch 
of networking fixes for 5.11, anyway. Would that be okay with you?