From 3ef0e5ba467366125f04b423f4638baca54a4fc1 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Fri, 20 Feb 2009 15:38:41 -0800 Subject: [PATCH] slab: introduce kzfree() 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 Reviewed-by: Pekka Enberg Cc: Matt Mackall Acked-by: Christoph Lameter Cc: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/slab.h | 1 + mm/util.c | 20 ++++++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/include/linux/slab.h b/include/linux/slab.h index f96d13c281e8..24c5602bee99 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -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 *); /* diff --git a/mm/util.c b/mm/util.c index cb00b748ce47..37eaccdf3054 100644 --- a/mm/util.c +++ b/mm/util.c @@ -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 -- 2.30.2