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kernel: kmem_ptr_validate considered harmful 

This is a nasty and error prone API. It is no longer used, remove it.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-07 17:49:17 +11:00
parent 786a5e15b6
commit ccd35fb9f4
5 changed files with 1 additions and 99 deletions
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2
include/linux/slab.h
View File

@ -106,8 +106,6 @@ int kmem_cache_shrink(struct kmem_cache *);
void kmem_cache_free(struct kmem_cache *, void *);
unsigned int kmem_cache_size(struct kmem_cache *);
const char *kmem_cache_name(struct kmem_cache *);
int kern_ptr_validate(const void *ptr, unsigned long size);
int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr);
/*
* Please use this macro to create slab caches. Simply specify the

32
mm/slab.c
View File

@ -2781,7 +2781,7 @@ static void slab_put_obj(struct kmem_cache *cachep, struct slab *slabp,
/*
* Map pages beginning at addr to the given cache and slab. This is required
* for the slab allocator to be able to lookup the cache and slab of a
* virtual address for kfree, ksize, kmem_ptr_validate, and slab debugging.
* virtual address for kfree, ksize, and slab debugging.
*/
static void slab_map_pages(struct kmem_cache *cache, struct slab *slab,
void *addr)
@ -3660,36 +3660,6 @@ void *kmem_cache_alloc_notrace(struct kmem_cache *cachep, gfp_t flags)
EXPORT_SYMBOL(kmem_cache_alloc_notrace);
#endif
/**
* kmem_ptr_validate - check if an untrusted pointer might be a slab entry.
* @cachep: the cache we're checking against
* @ptr: pointer to validate
*
* This verifies that the untrusted pointer looks sane;
* it is _not_ a guarantee that the pointer is actually
* part of the slab cache in question, but it at least
* validates that the pointer can be dereferenced and
* looks half-way sane.
*
* Currently only used for dentry validation.
*/
int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr)
{
unsigned long size = cachep->buffer_size;
struct page *page;
if (unlikely(!kern_ptr_validate(ptr, size)))
goto out;
page = virt_to_page(ptr);
if (unlikely(!PageSlab(page)))
goto out;
if (unlikely(page_get_cache(page) != cachep))
goto out;
return 1;
out:
return 0;
}
#ifdef CONFIG_NUMA
void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid)
{

5
mm/slob.c
View File

@ -678,11 +678,6 @@ int kmem_cache_shrink(struct kmem_cache *d)
}
EXPORT_SYMBOL(kmem_cache_shrink);
int kmem_ptr_validate(struct kmem_cache *a, const void *b)
{
return 0;
}
static unsigned int slob_ready __read_mostly;
int slab_is_available(void)

40
mm/slub.c
View File

@ -1917,17 +1917,6 @@ void kmem_cache_free(struct kmem_cache *s, void *x)
}
EXPORT_SYMBOL(kmem_cache_free);
/* Figure out on which slab page the object resides */
static struct page *get_object_page(const void *x)
{
struct page *page = virt_to_head_page(x);
if (!PageSlab(page))
return NULL;
return page;
}
/*
* Object placement in a slab is made very easy because we always start at
* offset 0. If we tune the size of the object to the alignment then we can
@ -2385,35 +2374,6 @@ error:
return 0;
}
/*
* Check if a given pointer is valid
*/
int kmem_ptr_validate(struct kmem_cache *s, const void *object)
{
struct page *page;
if (!kern_ptr_validate(object, s->size))
return 0;
page = get_object_page(object);
if (!page || s != page->slab)
/* No slab or wrong slab */
return 0;
if (!check_valid_pointer(s, page, object))
return 0;
/*
* We could also check if the object is on the slabs freelist.
* But this would be too expensive and it seems that the main
* purpose of kmem_ptr_valid() is to check if the object belongs
* to a certain slab.
*/
return 1;
}
EXPORT_SYMBOL(kmem_ptr_validate);
/*
* Determine the size of a slab object
*/

21
mm/util.c
View File

@ -186,27 +186,6 @@ void kzfree(const void *p)
}
EXPORT_SYMBOL(kzfree);
int kern_ptr_validate(const void *ptr, unsigned long size)
{
unsigned long addr = (unsigned long)ptr;
unsigned long min_addr = PAGE_OFFSET;
unsigned long align_mask = sizeof(void *) - 1;
if (unlikely(addr < min_addr))
goto out;
if (unlikely(addr > (unsigned long)high_memory - size))
goto out;
if (unlikely(addr & align_mask))
goto out;
if (unlikely(!kern_addr_valid(addr)))
goto out;
if (unlikely(!kern_addr_valid(addr + size - 1)))
goto out;
return 1;
out:
return 0;
}
/*
* strndup_user - duplicate an existing string from user space
* @s: The string to duplicate