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Subject[PATCH v1] [mm] Set page->slab_cache for every page allocated for a kmem_cache.
Date
It's reasonable to rely on the fact that for every page allocated for a
kmem_cache the |slab_cache| field points to that cache. Without that it's
hard to figure out which cache does an allocated object belong to.

Fixes: 55834c59098d0c5a97b0f324 ("mm: kasan: initial memory quarantine
implementation")
Signed-off-by: Alexander Potapenko <glider@google.com>
---
mm/slab.c | 7 ++++++-
mm/slub.c | 8 +++++---
2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index cc8bbc1..ac6c251 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2703,8 +2703,13 @@ static void slab_put_obj(struct kmem_cache *cachep,
static void slab_map_pages(struct kmem_cache *cache, struct page *page,
void *freelist)
{
- page->slab_cache = cache;
+ int i, nr_pages;
+ char *start = page_address(page);
+
page->freelist = freelist;
+ nr_pages = (1 << cache->gfporder);
+ for (i = 0; i < nr_pages; i++)
+ virt_to_page(start + PAGE_SIZE * i)->slab_cache = cache;
}

/*
diff --git a/mm/slub.c b/mm/slub.c
index 825ff45..fc75ddb 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1411,7 +1411,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
struct kmem_cache_order_objects oo = s->oo;
gfp_t alloc_gfp;
void *start, *p;
- int idx, order;
+ int idx, order, i, pages;

flags &= gfp_allowed_mask;

@@ -1442,9 +1442,9 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
stat(s, ORDER_FALLBACK);
}

+ pages = 1 << oo_order(oo);
if (kmemcheck_enabled &&
!(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
- int pages = 1 << oo_order(oo);

kmemcheck_alloc_shadow(page, oo_order(oo), alloc_gfp, node);

@@ -1461,13 +1461,15 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
page->objects = oo_objects(oo);

order = compound_order(page);
- page->slab_cache = s;
__SetPageSlab(page);
if (page_is_pfmemalloc(page))
SetPageSlabPfmemalloc(page);

start = page_address(page);

+ for (i = 0; i < pages; i++)
+ virt_to_page(start + PAGE_SIZE * i)->slab_cache = s;
+
if (unlikely(s->flags & SLAB_POISON))
memset(start, POISON_INUSE, PAGE_SIZE << order);

--
2.8.0.rc3.226.g39d4020
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