linux-kernel - Re: [PATCH] fs/nfsd: Delete invalid assignment statements in nfsd4_decode_exchange

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Date:   Sun, 22 Jul 2018 15:01:02 -0400
From:   Chuck Lever <chuck.lever@...cle.com>
To:     Trond Myklebust <trondmy@...merspace.com>
Cc:     "nixiaoming@...wei.com" <nixiaoming@...wei.com>,
        Bruce Fields <bfields@...ldses.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        "jlayton@...nel.org" <jlayton@...nel.org>
Subject: Re: [PATCH] fs/nfsd: Delete invalid assignment statements in
 nfsd4_decode_exchange_id



> On Jul 22, 2018, at 2:33 PM, Trond Myklebust <trondmy@...merspace.com> wrote:
> 
> On Sun, 2018-07-22 at 14:12 -0400, Chuck Lever wrote:
>>> On Jul 22, 2018, at 4:50 AM, nixiaoming <nixiaoming@...wei.com>
>>> wrote:
>>> 
>>> dummy = be32_to_cpup(p++);
>>> dummy = be32_to_cpup(p++);
>>> Assigning value to "dummy" here, but that stored value
>>> is overwritten before it can be used.
>>> 
>>> delete invalid assignment statements in nfsd4_decode_exchange_id
>>> 
>>> Signed-off-by: n00202754 <nixiaoming@...wei.com>
>>> ---
>>> fs/nfsd/nfs4xdr.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>> 
>>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
>>> index a96843c..8e78541 100644
>>> --- a/fs/nfsd/nfs4xdr.c
>>> +++ b/fs/nfsd/nfs4xdr.c
>>> @@ -1392,8 +1392,8 @@ nfsd4_decode_exchange_id(struct
>>> nfsd4_compoundargs *argp,
>>> 
>>> 		/* ssp_window and ssp_num_gss_handles */
>>> 		READ_BUF(8);
>>> -		dummy = be32_to_cpup(p++);
>>> -		dummy = be32_to_cpup(p++);
>>> +		be32_to_cpup(p++);
>>> +		be32_to_cpup(p++);
>> 
>> If these values are not used, what's the point of byte swapping them?
>> Surely "p += 2;" should be enough.
>> 
>> 
>>> 		break;
>>> 	default:
>>> 		goto xdr_error;
>> 
> 
> Given that the value of 'p' isn't used either, why not just delete
> those two lines altogether?

Sounds OK, READ_BUF is tracking progress through the buffer,
and it already updates "p" as a side-effect.

Might there be some nearby instances of open-coded "p" updates
that could also be removed, for similar reasons?


--
Chuck Lever