slab: introduce kzfree() (3ef0e5ba) · Commits · 戴 / test

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>

include/linux/slab.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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 *);

		/*

mm/util.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -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

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