Re: [PATCH -next,v2] gss_krb5: refactor code to return correct PTR_ERR in krb5_DK

[cuigaosheng <cuigaosheng1@huawei.com>]

Thanks for reviewing this patch.

I think this modification makes sense, for example, if 
crypto_sync_skcipher_setkey

return -ENOMEM, it's better to return -ENOMEM than to return -EINVAL,

just like elsewhere.

On 2024/7/12 22:28, Chuck Lever wrote:
> On Fri, Jul 12, 2024 at 09:39:08AM -0400, Chuck Lever wrote:
>> On Fri, Jul 12, 2024 at 03:24:23PM +0800, Gaosheng Cui wrote:
>>> Refactor the code in krb5_DK to return PTR_ERR when an error occurs.
>> My understanding of the current code is that if either
>> crypto_alloc_sync_skcipher() or crypto_sync_skcipher_blocksize()
>> fails, then krb5_DK() returns -EINVAL. At the only call site for
>> krb5_DK(), that return code is unconditionally discarded. Thus I
>> don't see that the proposed change is necessary or improves
>> anything.
> My understanding is wrong  ;-)
>
> The return code isn't discarded. A non-zero return code from
> krb5_DK() is carried back up the call stack. The logic in
> krb5_derive_key_v2() does not use the kernel's usual error flow
> form, so I missed this.
>
> However, it still isn't clear to me why the error behavior here
> needs to change. It's possible, for example, that -EINVAL is
> perfectly adequate to indicate when sync_skcipher() can't find the
> specified encryption algorithm (gk5e->encrypt_name).
>
> Specifying the wrong encryption type: -EINVAL. That makes sense.
>
>
>>> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
>>> ---
>>> v2: Update IS_ERR to PTR_ERR, thanks very much!
>>>   net/sunrpc/auth_gss/gss_krb5_keys.c | 8 ++++++--
>>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/net/sunrpc/auth_gss/gss_krb5_keys.c b/net/sunrpc/auth_gss/gss_krb5_keys.c
>>> index 4eb19c3a54c7..5ac8d06ab2c0 100644
>>> --- a/net/sunrpc/auth_gss/gss_krb5_keys.c
>>> +++ b/net/sunrpc/auth_gss/gss_krb5_keys.c
>>> @@ -164,10 +164,14 @@ static int krb5_DK(const struct gss_krb5_enctype *gk5e,
>>>   		goto err_return;
>>>   
>>>   	cipher = crypto_alloc_sync_skcipher(gk5e->encrypt_name, 0, 0);
>>> -	if (IS_ERR(cipher))
>>> +	if (IS_ERR(cipher)) {
>>> +		ret = PTR_ERR(cipher);
>>>   		goto err_return;
>>> +	}
>>> +
>>>   	blocksize = crypto_sync_skcipher_blocksize(cipher);
>>> -	if (crypto_sync_skcipher_setkey(cipher, inkey->data, inkey->len))
>>> +	ret = crypto_sync_skcipher_setkey(cipher, inkey->data, inkey->len);
>>> +	if (ret)
>>>   		goto err_free_cipher;
>>>   
>>>   	ret = -ENOMEM;
>>> -- 
>>> 2.25.1
>>>
>> -- 
>> Chuck Lever
>>