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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 <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Matt Mackall <[email protected]>
Cc: Nick Piggin <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Pekka Enberg 2010-04-07 19:23:40 +03:00 • committed by Linus Torvalds
commit fc1c183353
3 changed files with 23 additions and 12 deletions
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21
mm/util.c
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@ -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