mm/slab: use memzero_explicit() in kzfree()
authorWaiman Long <longman@redhat.com>
Fri, 26 Jun 2020 03:29:52 +0000 (20:29 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 26 Jun 2020 07:27:37 +0000 (00:27 -0700)
commit8982ae527fbef170ef298650c15d55a9ccd33973
treeb55c653e38fae2440851ee19f8d267cce71a625c
parentd7670879c5c4aa443d518fb234a9e5f30931efa3
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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/slab_common.c