linux-kernel - Re: [PATCH] slab: fix a crash by reading /proc/slab

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Date:   Sun, 7 Apr 2019 19:35:34 -1000
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Qian Cai <cai@....pw>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>, penberg@...nel.org,
        David Rientjes <rientjes@...gle.com>, iamjoonsoo.kim@....com,
        Tejun Heo <tj@...nel.org>, Linux-MM <linux-mm@...ck.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slab: fix a crash by reading /proc/slab_allocators

On Sat, Apr 6, 2019 at 12:59 PM Qian Cai <cai@....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.

Qian, how did you end up noticing and debugging this?

                 Linus