On 4/14/20 3:16 PM, Michal Suchánek wrote:
> On Tue, Apr 14, 2020 at 12:24:36PM -0400, Waiman Long wrote:
>> 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 <longman@xxxxxxxxxx>
>>>> ---
>>>> .../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.
> You already freed the key by now so not touching anything is not
> possible. The key is set to NULL on allocation failure so setting keylen
> to 0 should be redundant. However, setting keylen to 0 is consisent with
> not having a key, and it avoids the possibility of leaking the length
> later should that ever cause any problem.
OK, I can change it to clear the key length when the allocation failed
which isn't likely.
Cheers,
Longman
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