diff mbox series

[12/32] mm/slab: use memzero_explicit() in kzfree()

Message ID 20200626032952._ed4K7Snx%akpm@linux-foundation.org
State New
Headers show
Series [merged] mm-memcontrol-fix-do-not-put-the-css-reference.patch removed from -mm tree | expand

Commit Message

Andrew Morton June 26, 2020, 3:29 a.m. UTC 
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(-)
diff mbox series

Patch

--- 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);