From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Date: Tue, 14 Apr 2020 16:24:36 +0000 Subject: Re: [PATCH v2 2/2] crypto: Remove unnecessary memzero_explicit() Message-Id: List-Id: References: <20200413211550.8307-1-longman@redhat.com> <20200413222846.24240-1-longman@redhat.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Christophe Leroy , Andrew Morton , David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Linus Torvalds , Joe Perches , Matthew Wilcox , David Rientjes Cc: samba-technical@lists.samba.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, linux-sctp@vger.kernel.org, target-devel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, devel@driverdev.osuosl.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, x86@kernel.org, kasan-dev@googlegroups.com, cocci@systeme.lip6.fr, linux-wpan@vger.kernel.org, intel-wired-lan@lists.osuosl.org, linux-crypto@vger.kernel.org, linux-pm@vger.kernel.org, ecryptfs@vger.kernel.org, linux-nfs@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-cifs@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, tipc-discussion@lists.sourceforge.net, wireguard@lists.zx2c4.com, linux-ppp@vger.kernel.org, linux-integrity@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-btrfs@vger.kernel.org On 4/14/20 2:08 AM, Christophe Leroy wrote: > > > Le 14/04/2020 à 00:28, Waiman Long a écrit : >> Since kfree_sensitive() will do an implicit memzero_explicit(), there >> is no need to call memzero_explicit() before it. Eliminate those >> memzero_explicit() and simplify the call sites. For better correctness, >> the setting of keylen is also moved down after the key pointer check. >> >> Signed-off-by: Waiman Long >> --- >>   .../allwinner/sun8i-ce/sun8i-ce-cipher.c      | 19 +++++------------- >>   .../allwinner/sun8i-ss/sun8i-ss-cipher.c      | 20 +++++-------------- >>   drivers/crypto/amlogic/amlogic-gxl-cipher.c   | 12 +++-------- >>   drivers/crypto/inside-secure/safexcel_hash.c  |  3 +-- >>   4 files changed, 14 insertions(+), 40 deletions(-) >> >> diff --git a/drivers/crypto/allwinner/sun8i-ce/sun8i-ce-cipher.c >> b/drivers/crypto/allwinner/sun8i-ce/sun8i-ce-cipher.c >> index aa4e8fdc2b32..8358fac98719 100644 >> --- a/drivers/crypto/allwinner/sun8i-ce/sun8i-ce-cipher.c >> +++ b/drivers/crypto/allwinner/sun8i-ce/sun8i-ce-cipher.c >> @@ -366,10 +366,7 @@ void sun8i_ce_cipher_exit(struct crypto_tfm *tfm) >>   { >>       struct sun8i_cipher_tfm_ctx *op = crypto_tfm_ctx(tfm); >>   -    if (op->key) { >> -        memzero_explicit(op->key, op->keylen); >> -        kfree(op->key); >> -    } >> +    kfree_sensitive(op->key); >>       crypto_free_sync_skcipher(op->fallback_tfm); >>       pm_runtime_put_sync_suspend(op->ce->dev); >>   } >> @@ -391,14 +388,11 @@ int sun8i_ce_aes_setkey(struct crypto_skcipher >> *tfm, const u8 *key, >>           dev_dbg(ce->dev, "ERROR: Invalid keylen %u\n", keylen); >>           return -EINVAL; >>       } >> -    if (op->key) { >> -        memzero_explicit(op->key, op->keylen); >> -        kfree(op->key); >> -    } >> -    op->keylen = keylen; >> +    kfree_sensitive(op->key); >>       op->key = kmemdup(key, keylen, GFP_KERNEL | GFP_DMA); >>       if (!op->key) >>           return -ENOMEM; >> +    op->keylen = keylen; > > Does it matter at all to ensure op->keylen is not set when of->key is > NULL ? I'm not sure. > > But if it does, then op->keylen should be set to 0 when freeing op->key. My thinking is that if memory allocation fails, we just don't touch anything and return an error code. I will not explicitly set keylen to 0 in this case unless it is specified in the API documentation. Cheers, Longman