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mm: Convert check_heap_object() to use struct slab

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Ensure that we're not seeing a tail page inside __check_heap_object() by
converting to a slab instead of a page.  Take the opportunity to mark
the slab as const since we're not modifying it.  Also move the
declaration of __check_heap_object() to mm/slab.h so it's not available
to the wider kernel.

[ vbabka@suse.cz: in check_heap_object() only convert to struct slab for
  actual PageSlab pages; use folio as intermediate step instead of page ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
This commit is contained in:
Matthew Wilcox (Oracle) 2021-10-04 14:45:56 +01:00 • committed by Vlastimil Babka
parent 7213230af5
commit 0b3eb091d5
5 changed files with 30 additions and 26 deletions
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14
mm/slab.c
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@ -372,8 +372,8 @@ static void **dbg_userword(struct kmem_cache *cachep, void *objp)
static int slab_max_order = SLAB_MAX_ORDER_LO;
static bool slab_max_order_set __initdata;
static inline void *index_to_obj(struct kmem_cache *cache, struct page *page,
unsigned int idx)
static inline void *index_to_obj(struct kmem_cache *cache,
const struct page *page, unsigned int idx)
{
return page->s_mem + cache->size * idx;
}
@ -4166,8 +4166,8 @@ ssize_t slabinfo_write(struct file *file, const char __user *buffer,
* Returns NULL if check passes, otherwise const char * to name of cache
* to indicate an error.
*/
void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
bool to_user)
void __check_heap_object(const void *ptr, unsigned long n,
const struct slab *slab, bool to_user)
{
struct kmem_cache *cachep;
unsigned int objnr;
@ -4176,15 +4176,15 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
ptr = kasan_reset_tag(ptr);
/* Find and validate object. */
cachep = page->slab_cache;
objnr = obj_to_index(cachep, page, (void *)ptr);
cachep = slab->slab_cache;
objnr = obj_to_index(cachep, slab_page(slab), (void *)ptr);
BUG_ON(objnr >= cachep->num);
/* Find offset within object. */
if (is_kfence_address(ptr))
offset = ptr - kfence_object_start(ptr);
else
offset = ptr - index_to_obj(cachep, page, objnr) - obj_offset(cachep);
offset = ptr - index_to_obj(cachep, slab_page(slab), objnr) - obj_offset(cachep);
/* Allow address range falling entirely within usercopy region. */
if (offset >= cachep->useroffset &&