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Date:   Mon, 8 Apr 2019 15:15:11 +0000
From:   Christopher Lameter <cl@linux.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
cc:     Qian Cai <cai@lca.pw>, Andrew Morton <akpm@linux-foundation.org>,
        penberg@kernel.org, David Rientjes <rientjes@google.com>,
        iamjoonsoo.kim@lge.com, Tejun Heo <tj@kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] slab: fix a crash by reading /proc/slab_allocators
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On Sun, 7 Apr 2019, Linus Torvalds wrote:

> On Sat, Apr 6, 2019 at 12:59 PM Qian Cai <cai@lca.pw> wrote:
> >
> > The commit 510ded33e075 ("slab: implement slab_root_caches list")
> > changes the name of the list node within "struct kmem_cache" from
> > "list" to "root_caches_node", but leaks_show() still use the "list"
> > which causes a crash when reading /proc/slab_allocators.
>
> The patch does seem to be correct, and I have applied it.
>
> However, it does strike me that apparently this wasn't caught for two
> years. Which makes me wonder whether we should (once again) discuss
> just removing SLAB entirely, or at least removing the
> /proc/slab_allocators file. Apparently it has never been used in the
> last two years. At some point a "this can't have worked if  anybody
> ever tried to use it" situation means that the code should likely be
> excised.

This is only occurring with specially build kernels so that memory leaks
can be investigated. The same is done with other tools (kasan and friends)
today I guess and also the SLUB debugging tools are much more user
friendly. So this means that some esoteric debugging feature of SLAB was
broken.