RE: [PATCH] fs/nfsd: Delete invalid assignment statements in nfsd4_decode_exchange_id

From: Nixiaoming
Date: Sun Jul 22 2018 - 22:17:14 EST


On Mon, Jul 23, 2018 at 3:08 AM, Trond Myklebust wrote:
>On Sun, 2018-07-22 at 15:01 -0400, Chuck Lever wrote:
>> > On Jul 22, 2018, at 2:33 PM, Trond Myklebust <
>> > trondmy@xxxxxxxxxxxxxxx> wrote:
>> >
>> > On Sun, 2018-07-22 at 14:12 -0400, Chuck Lever wrote:
>> > > > On Jul 22, 2018, at 4:50 AM, nixiaoming <nixiaoming@xxxxxxxxxx>
>> > > > 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@xxxxxxxxxx>
>> > > > ---
>> > > > 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?
>>
>
>Probably, yes. I believe that we've said before (and Bruce agreed at
>the time) that we should get rid of READ_BUF() in knfsd as it tends to
>obfuscate these assignments to 'p'. Does anyone have any free cycles to
>work on that?
>
>--
>Trond Myklebust
>Linux NFS client maintainer, Hammerspace
>trond.myklebust@xxxxxxxxxxxxxxx
>
>

Thank you for your review,
I will update the patch as soon as possible based on your comments.

Thanks