Unlike SLAB, SLUB doesn't set PG_slab on tail pages, so if a user would
call free_pages() incorrectly on a object in a tail page, she will get
confused with the undefined result. Setting the flag would help her by
emitting a warning on bad_page() in such a case.
Reported-by: Sangseok Lee <sangseok.lee@xxxxxxx>
Signed-off-by: Namhyung Kim <namhyung.kim@xxxxxxx>
---
mm/slub.c | 12 ++++++++++--
1 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 33bab2aca882..575baacbec9b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1287,6 +1287,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
struct page *page;
struct kmem_cache_order_objects oo = s->oo;
gfp_t alloc_gfp;
+ int i;
flags &= gfp_allowed_mask;
@@ -1320,6 +1321,9 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
if (!page)
return NULL;
+ for (i = 0; i < 1 << oo_order(oo); i++)
+ __SetPageSlab(page + i);
+
if (kmemcheck_enabled
&& !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
int pages = 1 << oo_order(oo);
@@ -1369,7 +1373,6 @@ static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
inc_slabs_node(s, page_to_nid(page), page->objects);
page->slab = s;
- page->flags |= 1 << PG_slab;
start = page_address(page);
@@ -1396,6 +1399,7 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
{
int order = compound_order(page);
int pages = 1 << order;
+ int i;
if (kmem_cache_debug(s)) {
void *p;
@@ -1413,7 +1417,11 @@ static void __free_slab(struct kmem_cache *s, struct page *page)
NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
-pages);
- __ClearPageSlab(page);
+ for (i = 0; i < pages; i++) {
+ BUG_ON(!PageSlab(page + i));
+ __ClearPageSlab(page + i);
+ }
+
reset_page_mapcount(page);
if (current->reclaim_state)
current->reclaim_state->reclaimed_slab += pages;
--
1.7.9
--
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