linux-kernel - Re: RFC v2: post-init-read-only protection for data allocated dynamically

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Message-ID: <20170510074518.GE31466@dhcp22.suse.cz>
Date:   Wed, 10 May 2017 09:45:19 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Igor Stoppa <igor.stoppa@...wei.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: RFC v2: post-init-read-only protection for data allocated
 dynamically

On Fri 05-05-17 15:19:19, Igor Stoppa wrote:
> 
> 
> On 04/05/17 17:01, Michal Hocko wrote:
> > On Thu 04-05-17 16:37:55, Igor Stoppa wrote:
> 
> [...]
> 
> >> The disadvantage is that anything can happen, undetected, while the seal
> >> is lifted.
> > 
> > Yes and I think this makes it basically pointless
> 
> ok, this goes a bit beyond what I had in mind initially, but I see your
> point
> 
> [...]
> 
> > Just to make my proposal more clear. I suggest the following workflow
> > 
> > cache = kmem_cache_create(foo, object_size, ..., SLAB_SEAL);
> >
> > obj = kmem_cache_alloc(cache, gfp_mask);
> > init_obj(obj)
> > [more allocations]
> > kmem_cache_seal(cache);
> 
> In case one doesn't want the feature, at which point would it be disabled?
> 
> * not creating the slab
> * not sealing it
> * something else?

If the sealing would be disabled then sealing would be a noop.

-- 
Michal Hocko
SUSE Labs