The patch titled
Subject: slub: add back check for free nonslab objects
has been added to the -mm tree. Its filename is
slub-add-back-check-for-free-nonslab-objects.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/slub-add-back-check-for-free-nonslab-objects.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/slub-add-back-check-for-free-nonslab-objects.patch
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------------------------------------------------------
From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Subject: slub: add back check for free nonslab objects
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.
Link: https://lkml.kernel.org/r/20210927122646.91934-1-wangkefeng.wang@xxxxxxxxxx
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rienjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/mm/slub.c~slub-add-back-check-for-free-nonslab-objects
+++ a/mm/slub.c
@@ -3522,7 +3522,11 @@ static inline void free_nonslab_page(str
{
unsigned int order = compound_order(page);
- VM_BUG_ON_PAGE(!PageCompound(page), page);
+ if (WARN_ON(!PageCompound(page))) {
+ dump_page(page, "invalid free nonslab page");
+ pr_warn("object pointer: 0x%p\n", object);
+ }
+
kfree_hook(object);
mod_lruvec_page_state(page, NR_SLAB_UNRECLAIMABLE_B, -(PAGE_SIZE << order));
__free_pages(page, order);
_
Patches currently in -mm which might be from wangkefeng.wang@xxxxxxxxxx are
slub-add-back-check-for-free-nonslab-objects.patch
mm-nommu-kill-arch_get_unmapped_area.patch
