Re: [RFC PATCH 4/5] mm, slub: make remaining slub_debug related attributes read-only

Kees Cook
2020-06-05T21:07:15Z

On Tue, Jun 02, 2020 at 04:15:18PM +0200, Vlastimil Babka wrote:
> SLUB_DEBUG creates several files under /sys/kernel/slab/<cache>/ that can be
> read to check if the respective debugging options are enabled for given cache.
> Some options, namely sanity_checks, trace, and failslab can be also enabled and
> disabled at runtime by writing into the files.
>
> The runtime toggling is racy. Some options disable __CMPXCHG_DOUBLE when
> enabled, which means that in case of concurrent allocations, some can still use
> __CMPXCHG_DOUBLE and some not, leading to potential corruption. The s->flags
> field is also not updated or checked atomically. The simplest solution is to
> remove the runtime toggling. The extended slub_debug boot parameter syntax
> introduced by earlier patch should allow to fine-tune the debugging
> configuration during boot with same granularity.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Reviewed-by: Kees Cook <keescook@chromium.org>

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Kees Cook