From: Michal Hocko <mhocko@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Howells <dhowells@redhat.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Joe Perches <joe@perches.com>,
Matthew Wilcox <willy@infradead.org>,
David Rientjes <rientjes@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Dan Carpenter <dan.carpenter@oracle.com>,
David Sterba <dsterba@suse.cz>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
linux-mm@kvack.org, keyrings@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-pm@vger.kernel.org,
linux-stm32@st-md-mailman.stormreply.com,
linux-amlogic@lists.infradead.org,
linux-mediatek@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org,
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linux-integrity@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v4 1/3] mm/slab: Use memzero_explicit() in kzfree()
Date: Tue, 16 Jun 2020 08:42:08 +0200 [thread overview]
Message-ID: <20200616064208.GA9499@dhcp22.suse.cz> (raw)
In-Reply-To: <20200616015718.7812-2-longman@redhat.com>
On Mon 15-06-20 21:57:16, Waiman Long wrote:
> 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@vger.kernel.org
> Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Although I am not really sure this is a stable material. Is there any
known instance where the memset was optimized out from kzfree?
> ---
> 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
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-06-16 6:42 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-16 1:57 [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive() Waiman Long
2020-06-16 1:57 ` [PATCH v4 1/3] mm/slab: Use memzero_explicit() in kzfree() Waiman Long
2020-06-16 3:30 ` Eric Biggers
2020-06-16 13:05 ` Waiman Long
2020-06-16 15:46 ` David Howells
2020-06-16 6:42 ` Michal Hocko [this message]
2020-06-16 9:08 ` Dan Carpenter
2020-06-16 1:57 ` [PATCH v4 2/3] mm, treewide: Rename kzfree() to kfree_sensitive() Waiman Long
2020-06-16 14:26 ` Dan Carpenter
2020-06-16 15:05 ` Waiman Long
2020-06-16 1:57 ` [PATCH v4 3/3] btrfs: Use kfree() in btrfs_ioctl_get_subvol_info() Waiman Long
2020-06-16 14:48 ` David Sterba
2020-06-16 15:05 ` Waiman Long
2020-06-16 18:53 ` [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive() Joe Perches
2020-06-16 19:43 ` Waiman Long
2020-06-16 19:46 ` Jason A. Donenfeld
2020-06-16 20:01 ` Waiman Long
2020-06-16 21:14 ` Matthew Wilcox
2020-06-16 23:01 ` David Sterba
2020-06-17 0:37 ` Matthew Wilcox
2020-06-17 7:12 ` Michal Hocko
2020-06-17 11:08 ` Matthew Wilcox
2020-06-17 11:31 ` Michal Hocko
2020-06-17 12:23 ` Matthew Wilcox
2020-06-17 12:55 ` Michal Hocko
2020-06-17 8:03 ` Jo -l
2020-06-17 21:31 ` Denis Efremov
2020-06-17 23:12 ` Joe Perches
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