netdev - [PATCH v4 1/3] mm/slab: Use memzero

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Date:   Mon, 15 Jun 2020 21:57:16 -0400
From:   Waiman Long <longman@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Joe Perches <joe@...ches.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>
Cc:     Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        David Sterba <dsterba@...e.cz>,
        "Jason A . Donenfeld" <Jason@...c4.com>, linux-mm@...ck.org,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-amlogic@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-ppp@...r.kernel.org, wireguard@...ts.zx2c4.com,
        linux-wireless@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-cifs@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, ecryptfs@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-bluetooth@...r.kernel.org,
        linux-wpan@...r.kernel.org, linux-sctp@...r.kernel.org,
        linux-nfs@...r.kernel.org, tipc-discussion@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, Waiman Long <longman@...hat.com>,
        stable@...r.kernel.org
Subject: [PATCH v4 1/3] 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 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: stable@...r.kernel.org
Signed-off-by: Waiman Long <longman@...hat.com>
---
 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