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slab: introduce kzfree()

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kzfree() is a wrapper for kfree() that additionally zeroes the underlying
memory before releasing it to the slab allocator.

Currently there is code which memset()s the memory region of an object
before releasing it back to the slab allocator to make sure
security-sensitive data are really zeroed out after use.

These callsites can then just use kzfree() which saves some code, makes
users greppable and allows for a stupid destructor that isn't necessarily
aware of the actual object size.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Matt Mackall <mpm@selenic.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2009-02-20 15:38:41 -08:00 committed by Linus Torvalds
parent d9190913b7
commit 3ef0e5ba46
2 changed files with 21 additions and 0 deletions
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1
include/linux/slab.h
View File

@ -127,6 +127,7 @@ int kmem_ptr_validate(struct kmem_cache *cachep, const void *ptr);
void * __must_check __krealloc(const void *, size_t, gfp_t);
void * __must_check krealloc(const void *, size_t, gfp_t);
void kfree(const void *);
void kzfree(const void *);
size_t ksize(const void *);
/*

20
mm/util.c
View File

@ -129,6 +129,26 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags)
}
EXPORT_SYMBOL(krealloc);
/**
* kzfree - like kfree but zero memory
* @p: object to free memory of
*
* The memory of the object @p points to is zeroed before freed.
* If @p is %NULL, kzfree() does nothing.
*/
void kzfree(const void *p)
{
size_t ks;
void *mem = (void *)p;
if (unlikely(ZERO_OR_NULL_PTR(mem)))
return;
ks = ksize(mem);
memset(mem, 0, ks);
kfree(mem);
}
EXPORT_SYMBOL(kzfree);
/*
* strndup_user - duplicate an existing string from user space
* @s: The string to duplicate