fs/nfsd: Delete invalid assignment statements in nfsd4_decode_exchange_id
diff mbox series

Message ID 20180722085044.50701-1-nixiaoming@huawei.com
State New
Headers show
Series
  • fs/nfsd: Delete invalid assignment statements in nfsd4_decode_exchange_id
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Commit Message

Xiaoming Ni July 22, 2018, 8:50 a.m. UTC
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@huawei.com>
---
 fs/nfsd/nfs4xdr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Chuck Lever July 22, 2018, 6:12 p.m. UTC | #1
> On Jul 22, 2018, at 4:50 AM, nixiaoming <nixiaoming@huawei.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@huawei.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;

--
Chuck Lever



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Trond Myklebust July 22, 2018, 6:33 p.m. UTC | #2
On Sun, 2018-07-22 at 14:12 -0400, Chuck Lever wrote:
> > On Jul 22, 2018, at 4:50 AM, nixiaoming <nixiaoming@huawei.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@huawei.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?
Chuck Lever July 22, 2018, 7:01 p.m. UTC | #3
> On Jul 22, 2018, at 2:33 PM, Trond Myklebust <trondmy@hammerspace.com> wrote:
> 
> On Sun, 2018-07-22 at 14:12 -0400, Chuck Lever wrote:
>>> On Jul 22, 2018, at 4:50 AM, nixiaoming <nixiaoming@huawei.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@huawei.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



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Trond Myklebust July 22, 2018, 7:08 p.m. UTC | #4
On Sun, 2018-07-22 at 15:01 -0400, Chuck Lever wrote:
> > On Jul 22, 2018, at 2:33 PM, Trond Myklebust <
> > trondmy@hammerspace.com> wrote:
> > 
> > On Sun, 2018-07-22 at 14:12 -0400, Chuck Lever wrote:
> > > > On Jul 22, 2018, at 4:50 AM, nixiaoming <nixiaoming@huawei.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@huawei.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?
> 

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?
Xiaoming Ni July 23, 2018, 2:16 a.m. UTC | #5
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@hammerspace.com> wrote:
>> > 
>> > On Sun, 2018-07-22 at 14:12 -0400, Chuck Lever wrote:
>> > > > On Jul 22, 2018, at 4:50 AM, nixiaoming <nixiaoming@huawei.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@huawei.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?
>> 
>
>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@hammerspace.com
>
>

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

Thanks

Patch
diff mbox series

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++);
 		break;
 	default:
 		goto xdr_error;