linux-kernel - Re: [PATCH] cifs: Fix smbencrypt() to stop pointing a scatterlist at the stack

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Date:   Wed, 14 Dec 2016 02:19:03 -0600
From:   Steve French <smfrench@...il.com>
To:     Jeff Layton <jlayton@...hat.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-usb@...r.kernel.org,
        Steve French <sfrench@...ba.org>,
        Eric Biggers <ebiggers3@...il.com>,
        linux-crypto@...r.kernel.org,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Stephan Mueller <smueller@...onox.de>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>
Subject: Re: [PATCH] cifs: Fix smbencrypt() to stop pointing a scatterlist at
 the stack

merged into cifs-2.6.git for-next

On Tue, Dec 13, 2016 at 7:07 AM, Jeff Layton <jlayton@...hat.com> wrote:
> On Mon, 2016-12-12 at 12:54 -0800, Andy Lutomirski wrote:
>> smbencrypt() points a scatterlist to the stack, which is breaks if
>> CONFIG_VMAP_STACK=y.
>>
>> Fix it by switching to crypto_cipher_encrypt_one().  The new code
>> should be considerably faster as an added benefit.
>>
>> This code is nearly identical to some code that Eric Biggers
>> suggested.
>>
>> Cc: stable@...r.kernel.org # 4.9 only
>> Reported-by: Eric Biggers <ebiggers3@...il.com>
>> Signed-off-by: Andy Lutomirski <luto@...nel.org>
>> ---
>>
>> Compile-tested only.
>>
>> fs/cifs/smbencrypt.c | 40 ++++++++--------------------------------
>>  1 file changed, 8 insertions(+), 32 deletions(-)
>>
>> diff --git a/fs/cifs/smbencrypt.c b/fs/cifs/smbencrypt.c
>> index 699b7868108f..c12bffefa3c9 100644
>> --- a/fs/cifs/smbencrypt.c
>> +++ b/fs/cifs/smbencrypt.c
>> @@ -23,7 +23,7 @@
>>     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>>  */
>>
>> -#include <crypto/skcipher.h>
>> +#include <linux/crypto.h>
>>  #include <linux/module.h>
>>  #include <linux/slab.h>
>>  #include <linux/fs.h>
>> @@ -69,46 +69,22 @@ str_to_key(unsigned char *str, unsigned char *key)
>>  static int
>>  smbhash(unsigned char *out, const unsigned char *in, unsigned char *key)
>>  {
>> -     int rc;
>>       unsigned char key2[8];
>> -     struct crypto_skcipher *tfm_des;
>> -     struct scatterlist sgin, sgout;
>> -     struct skcipher_request *req;
>> +     struct crypto_cipher *tfm_des;
>>
>>       str_to_key(key, key2);
>>
>> -     tfm_des = crypto_alloc_skcipher("ecb(des)", 0, CRYPTO_ALG_ASYNC);
>> +     tfm_des = crypto_alloc_cipher("des", 0, 0);
>>       if (IS_ERR(tfm_des)) {
>> -             rc = PTR_ERR(tfm_des);
>> -             cifs_dbg(VFS, "could not allocate des crypto API\n");
>> -             goto smbhash_err;
>> -     }
>> -
>> -     req = skcipher_request_alloc(tfm_des, GFP_KERNEL);
>> -     if (!req) {
>> -             rc = -ENOMEM;
>>               cifs_dbg(VFS, "could not allocate des crypto API\n");
>> -             goto smbhash_free_skcipher;
>> +             return PTR_ERR(tfm_des);
>>       }
>>
>> -     crypto_skcipher_setkey(tfm_des, key2, 8);
>> -
>> -     sg_init_one(&sgin, in, 8);
>> -     sg_init_one(&sgout, out, 8);
>> +     crypto_cipher_setkey(tfm_des, key2, 8);
>> +     crypto_cipher_encrypt_one(tfm_des, out, in);
>> +     crypto_free_cipher(tfm_des);
>>
>> -     skcipher_request_set_callback(req, 0, NULL, NULL);
>> -     skcipher_request_set_crypt(req, &sgin, &sgout, 8, NULL);
>> -
>> -     rc = crypto_skcipher_encrypt(req);
>> -     if (rc)
>> -             cifs_dbg(VFS, "could not encrypt crypt key rc: %d\n", rc);
>> -
>> -     skcipher_request_free(req);
>> -
>> -smbhash_free_skcipher:
>> -     crypto_free_skcipher(tfm_des);
>> -smbhash_err:
>> -     return rc;
>> +     return 0;
>>  }
>>
>>  static int
>
> Acked-by: Jeff Layton <jlayton@...hat.com>
> --
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-- 
Thanks,

Steve