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Date: Tue, 28 Sep 2021 08:09:17 -0700 From: Shakeel Butt <shakeelb@...gle.com> To: Kefeng Wang <wangkefeng.wang@...wei.com> Cc: Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, Andrew Morton <akpm@...ux-foundation.org>, Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Matthew Wilcox <willy@...radead.org> Subject: Re: [PATCH v2] slub: Add back check for free nonslab objects On Mon, Sep 27, 2021 at 5:24 AM Kefeng Wang <wangkefeng.wang@...wei.com> wrote: > > After commit ("f227f0faf63b slub: fix unreclaimable slab stat for bulk > free"), the check for free nonslab page is replaced by VM_BUG_ON_PAGE, > which only check with CONFIG_DEBUG_VM enabled, but this config may > impact performance, so it only for debug. > > Commit ("0937502af7c9 slub: Add check for kfree() of non slab objects.") > add the ability, which should be needed in any configs to catch the > invalid free, they even could be potential issue, eg, memory corruption, > use after free and double-free, so replace VM_BUG_ON_PAGE to WARN_ON, add > dump_page() and object address printing to help use to debug the issue. > > Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com> > --- > v2: Add object address printing suggested by Matthew Wilcox > > mm/slub.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 3095b889fab4..157973e22faf 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3522,7 +3522,11 @@ static inline void free_nonslab_page(struct page *page, void *object) > { > unsigned int order = compound_order(page); > > - VM_BUG_ON_PAGE(!PageCompound(page), page); > + if (WARN_ON(!PageCompound(page))) { If there is a problem then this would be too noisy. Why not WARN_ON_ONCE()? > + dump_page(page, "invalid free nonslab page"); > + pr_warn("object pointer: 0x%p\n", object); Actually why not add 'once' semantics for the whole if-block? > + } > + > kfree_hook(object); > mod_lruvec_page_state(page, NR_SLAB_UNRECLAIMABLE_B, -(PAGE_SIZE << order)); > __free_pages(page, order); > -- > 2.26.2 >
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