From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v3] kvmalloc: always use vmalloc if CONFIG_DEBUG_SG
Date: Tue, 24 Apr 2018 10:16:51 -0700
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To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Christoph Lameter <cl@linux.com>, dm-devel@redhat.com, eric.dumazet@gmail.com, mst@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Michal Hocko <mhocko@kernel.org>, Pekka Enberg <penberg@kernel.org>, linux-mm@kvack.org, edumazet@google.com, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, virtualization@lists.linux-foundation.org, David Miller <davem@davemloft.net>, Vlastimil Babka <vbabka@suse.cz>
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On Tue, Apr 24, 2018 at 08:29:14AM -0400, Mikulas Patocka wrote:
> 
> 
> On Mon, 23 Apr 2018, Matthew Wilcox wrote:
> 
> > On Mon, Apr 23, 2018 at 08:06:16PM -0400, Mikulas Patocka wrote:
> > > Some bugs (such as buffer overflows) are better detected
> > > with kmalloc code, so we must test the kmalloc path too.
> > 
> > Well now, this brings up another item for the collective TODO list --
> > implement redzone checks for vmalloc.  Unless this is something already
> > taken care of by kasan or similar.
> 
> The kmalloc overflow testing is also not ideal - it rounds the size up to 
> the next slab size and detects buffer overflows only at this boundary.
> 
> Some times ago, I made a "kmalloc guard" patch that places a magic number 
> immediatelly after the requested size - so that it can detect overflows at 
> byte boundary 
> ( https://www.redhat.com/archives/dm-devel/2014-September/msg00018.html )
> 
> That patch found a bug in crypto code:
> ( http://lkml.iu.edu/hypermail/linux/kernel/1409.1/02325.html )

Is it still worth doing this, now we have kasan?