Subject: [PATCH v4 1/3] mm/slab: Use memzero_explicit() in kzfree()

From: Waiman Long <[email-masked]>
Date: Mon, 15 Jun 2020 21:57:16 -0400

The kzfree() function is normally used to clear some sensitive
information, like encryption keys, in the buffer before freeing it back
to the pool. Memset() is currently used for the buffer clearing. However,
it is entirely possible that the compiler may choose to optimize away the
memory clearing especially if LTO is being used. To make sure that this
optimization will not happen, memzero_explicit(), which is introduced
in v3.18, is now used in kzfree() to do the clearing.

Fixes: 3ef0e5ba4673 ("slab: introduce kzfree()")
Cc: [email-masked]
Signed-off-by: Waiman Long <[email-masked]>
---
 mm/slab_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 9e72ba224175..37d48a56431d 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1726,7 +1726,7 @@ void kzfree(const void *p)
 	if (unlikely(ZERO_OR_NULL_PTR(mem)))
 		return;
 	ks = ksize(mem);
-	memset(mem, 0, ks);
+	memzero_explicit(mem, ks);
 	kfree(mem);
 }
 EXPORT_SYMBOL(kzfree);
-- 
2.18.1