Re: [PATCH] slab: fix a crash by reading /proc/slab_allocators

["Tobin C. Harding" <me@tobin.cc>]

On Sun, Apr 07, 2019 at 07:35:34PM -1000, 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.

The bug doesn't trigger on every read of /proc/slab_allocators (as noted
later in this thread by Qian).  I tried to repro it with a bunch of
different configs and often `cat /proc/slab_allocators` just returns
empty.

I've got a patchset ready to go sitting in my tree that removes SLAB, I
could just send it to start the conversation :)


	Tobin