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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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13
mm/usercopy.c
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@ -20,6 +20,7 @@
#include <linux/atomic.h>
#include <linux/jump_label.h>
#include <asm/sections.h>
#include "slab.h"
/*
* Checks if a given pointer and length is contained by the current
@ -223,7 +224,7 @@ static inline void check_page_span(const void *ptr, unsigned long n,
static inline void check_heap_object(const void *ptr, unsigned long n,
bool to_user)
{
struct page *page;
struct folio *folio;
if (!virt_addr_valid(ptr))
return;
@ -231,16 +232,16 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
/*
* When CONFIG_HIGHMEM=y, kmap_to_page() will give either the
* highmem page or fallback to virt_to_page(). The following
* is effectively a highmem-aware virt_to_head_page().
* is effectively a highmem-aware virt_to_slab().
*/
page = compound_head(kmap_to_page((void *)ptr));
folio = page_folio(kmap_to_page((void *)ptr));
if (PageSlab(page)) {
if (folio_test_slab(folio)) {
/* Check slab allocator for flags and size. */
__check_heap_object(ptr, n, page, to_user);
__check_heap_object(ptr, n, folio_slab(folio), to_user);
} else {
/* Verify object does not incorrectly span multiple pages. */
check_page_span(ptr, n, page, to_user);
check_page_span(ptr, n, folio_page(folio, 0), to_user);
}
}