lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 1 May 2018 17:36:26 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        David Miller <davem@...emloft.net>, linux-mm@...ck.org,
        eric.dumazet@...il.com, edumazet@...gle.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        mst@...hat.com, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org, dm-devel@...hat.com,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM

On Tue, 24 Apr 2018 12:33:01 -0400 (EDT) Mikulas Patocka <mpatocka@...hat.com> wrote:

> 
> 
> On Tue, 24 Apr 2018, Michal Hocko wrote:
> 
> > On Tue 24-04-18 11:30:40, Mikulas Patocka wrote:
> > > 
> > > 
> > > On Tue, 24 Apr 2018, Michal Hocko wrote:
> > > 
> > > > On Mon 23-04-18 20:25:15, Mikulas Patocka wrote:
> > > > 
> > > > > Fixing __vmalloc code 
> > > > > is easy and it doesn't require cooperation with maintainers.
> > > > 
> > > > But it is a hack against the intention of the scope api.
> > > 
> > > It is not!
> > 
> > This discussion simply doesn't make much sense it seems. The scope API
> > is to document the scope of the reclaim recursion critical section. That
> > certainly is not a utility function like vmalloc.
> 
> That 15-line __vmalloc bugfix doesn't prevent you (or any other kernel 
> developer) from converting the code to the scope API. You make nonsensical 
> excuses.
> 

Fun thread!

Winding back to the original problem, I'd state it as

- Caller uses kvmalloc() but passes the address into vmalloc-naive
  DMA API and

- Caller uses kvmalloc() but passes the address into kfree()

Yes?

If so, then...

Is there a way in which, in the kvmalloc-called-kmalloc path, we can
tag the slab-allocated memory with a "this memory was allocated with
kvmalloc()" flag?  I *think* there's extra per-object storage available
with suitable slab/slub debugging options?  Perhaps we could steal one
bit from the redzone, dunno.

If so then we can

a) set that flag in kvmalloc() if the kmalloc() call succeeded

b) check for that flag in the DMA code, WARN if it is set.

c) in kvfree(), clear that flag before calling kfree()

d) in kfree(), check for that flag and go WARN() if set.

So both potential bugs are detected all the time, dependent upon
CONFIG_SLUB_DEBUG (and perhaps other slub config options).

Powered by blists - more mailing lists