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slab: Generify kernel pointer validation

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As suggested by Linus, introduce a kern_ptr_validate() helper that does some
sanity checks to make sure a pointer is a valid kernel pointer.  This is a
preparational step for fixing SLUB kmem_ptr_validate().

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Pekka Enberg 2010-04-07 19:23:40 +03:00 committed by Linus Torvalds
parent 4dc86ae1f9
commit fc1c183353
3 changed files with 23 additions and 12 deletions
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1
include/linux/slab.h
View File

@ -106,6 +106,7 @@ 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);
/*

13
mm/slab.c
View File

@ -3602,21 +3602,10 @@ EXPORT_SYMBOL(kmem_cache_alloc_notrace);
*/
int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr)
{
unsigned long addr = (unsigned long)ptr;
unsigned long min_addr = PAGE_OFFSET;
unsigned long align_mask = BYTES_PER_WORD - 1;
unsigned long size = cachep->buffer_size;
struct page *page;
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)))
if (unlikely(!kern_ptr_validate(ptr, size)))
goto out;
page = virt_to_page(ptr);
if (unlikely(!PageSlab(page)))

21
mm/util.c
View File

@ -186,6 +186,27 @@ 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