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authorJohannes Weiner <hannes@cmpxchg.org>2009-02-20 15:38:41 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-02-20 17:57:48 -0800
commit3ef0e5ba467366125f04b423f4638baca54a4fc1 (patch)
treecfe7b95c7b19b1d5b2a8534fa9791d6026e49dcd
parentd9190913b71831f5e3d04de62cfb1fd069a9db35 (diff)
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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 <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>
-rw-r--r--include/linux/slab.h1
-rw-r--r--mm/util.c20
2 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/slab.h b/include/linux/slab.h
index f96d13c281e..24c5602bee9 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 cb00b748ce4..37eaccdf305 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