+ mm-slab-use-memzero_explicit-in-kzfree.patch added to -mm tree

+ mm-slab-use-memzero_explicit-in-kzfree.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/slab: use memzero_explicit() in kzfree()
has been added to the -mm tree.  Its filename is
     mm-slab-use-memzero_explicit-in-kzfree.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-slab-use-memzero_explicit-in-kzfree.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-slab-use-memzero_explicit-in-kzfree.patch

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------------------------------------------------------
From: Waiman Long <longman@redhat.com>
Subject: mm/slab: use memzero_explicit() in kzfree()

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 buffer clearing.  However
unlikely, there is still a non-zero probability that the compiler may
choose to optimize away the memory clearing especially if LTO is being
used in the future.  To make sure that this optimization will never
happen, memzero_explicit(), which is introduced in v3.18, is now used in
kzfree() to future-proof it.

Link: http://lkml.kernel.org/r/20200616154311.12314-2-longman@redhat.com
Fixes: 3ef0e5ba4673 ("slab: introduce kzfree()")
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Joe Perches <joe@perches.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Jason A . Donenfeld" <Jason@zx2c4.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slab_common.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/slab_common.c~mm-slab-use-memzero_explicit-in-kzfree
+++ a/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);
_

Patches currently in -mm which might be from longman@redhat.com are

mm-slab-use-memzero_explicit-in-kzfree.patch
mm-treewide-rename-kzfree-to-kfree_sensitive.patch