On Fri, Sep 6, 2013 at 5:30 PM, Tyler Hicks <tyhicks@xxxxxxxxxxxxx> wrote:
> On 2013-08-13 15:02:27, Kees Cook wrote:
>> It might be possible for two callers to race the mutex lock after the
>> NULL ctx check. Instead, move the lock above the check so there isn't
>> the possibility of leaking a crypto ctx. Additionally, report the full
>> algo name when failing.
>>
>> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
>
> Thanks, Kees!
>
> I've pushed this to my next branch and it'll be included in a pull
> request early next week.
>
> I made one small change to this patch. See below.
>
>> ---
>> fs/ecryptfs/crypto.c | 11 ++++++-----
>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
>> index d107576..c134346 100644
>> --- a/fs/ecryptfs/crypto.c
>> +++ b/fs/ecryptfs/crypto.c
>> @@ -618,27 +618,28 @@ int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
>> "key_size_bits = [%zd]\n",
>> crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
>> crypt_stat->key_size << 3);
>> + mutex_lock(&crypt_stat->cs_tfm_mutex);
>> if (crypt_stat->tfm) {
>> rc = 0;
>> - goto out;
>> + goto out_unlock;
>> }
>> - mutex_lock(&crypt_stat->cs_tfm_mutex);
>> rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
>> crypt_stat->cipher, "cbc");
>> if (rc)
>> goto out_unlock;
>> crypt_stat->tfm = crypto_alloc_ablkcipher(full_alg_name, 0, 0);
>> - kfree(full_alg_name);
>> if (IS_ERR(crypt_stat->tfm)) {
>> rc = PTR_ERR(crypt_stat->tfm);
>> crypt_stat->tfm = NULL;
>> ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
>> "Error initializing cipher [%s]\n",
>> - crypt_stat->cipher);
>> - goto out_unlock;
>> + full_alg_name);
>> + goto out_free;
>> }
>> crypto_ablkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
>> rc = 0;
>> +out_free:
>> + kfree(full_alg_name);
>> out_unlock:
>> mutex_unlock(&crypt_stat->cs_tfm_mutex);
>> out:
>
> The out label is no longer used. I removed it when I committed this
> patch.
Ah! Yes, good call. Thanks,
-Kees
--
Kees Cook
Chrome OS Security
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