linux-kernel - [PATCH 5.7 230/265] mm/slab: use memzero

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200629151818.2493727-231-sashal@kernel.org>
Date:   Mon, 29 Jun 2020 11:17:43 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Waiman Long <longman@...hat.com>, Michal Hocko <mhocko@...e.com>,
        David Howells <dhowells@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Joe Perches <joe@...ches.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 5.7 230/265] mm/slab: use memzero_explicit() in kzfree()

From: Waiman Long <longman@...hat.com>

commit 8982ae527fbef170ef298650c15d55a9ccd33973 upstream.

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@...hat.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Cc: David Howells <dhowells@...hat.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc: James Morris <jmorris@...ei.org>
Cc: "Serge E. Hallyn" <serge@...lyn.com>
Cc: Joe Perches <joe@...ches.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Cc: "Jason A . Donenfeld" <Jason@...c4.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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 9e72ba2241750..37d48a56431d0 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);
-- 
2.25.1