Re: [PATCH] nfsd: make calculate reserved space correctly

[Kinglong Mee <kinglongmee@gmail.com>]

On 12/13/2013 12:24 AM, J. Bruce Fields wrote:
> On Mon, Dec 09, 2013 at 07:31:21PM +0800, Kinglong Mee wrote:
>> rpcsec_gss_oid is defined as below, So, must using XDR_LEN to calculate reserved space.
>> When len is not the multiples of 4, client will get bad data.
> 
> Looking at the definition of RESERVE_SPACE: first, it doesn't actually
> advance any pointers, all it does is an overflow check, so there
> shouldn't be data corruption unless we're at the end of a page (which
> shouldn't happen here).  Second, RESERVE_SPACE actually rounds up for
> is, so we wouldn't hit that problem anyway.

Yes.

> 
> Nevertheless, agreed that it's probably good practice to round up here
> as well.

Thank you.

thanks,
Kinglong Mee

> 
> --b.
> 
>>
>> struct rpcsec_gss_oid {
>>         unsigned int    len;
>>         u8              data[GSS_OID_MAX_LEN];
>> };
>>
>> Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
>> ---
>>  fs/nfsd/nfs4xdr.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
>> index b0b886e..a57e67d 100644
>> --- a/fs/nfsd/nfs4xdr.c
>> +++ b/fs/nfsd/nfs4xdr.c
>> @@ -3233,7 +3233,7 @@ nfsd4_do_encode_secinfo(struct nfsd4_compoundres *resp,
>>  
>>  		if (rpcauth_get_gssinfo(pf, &info) == 0) {
>>  			supported++;
>> -			RESERVE_SPACE(4 + 4 + info.oid.len + 4 + 4);
>> +			RESERVE_SPACE(4 + 4 + XDR_LEN(info.oid.len) + 4 + 4);
>>  			WRITE32(RPC_AUTH_GSS);
>>  			WRITE32(info.oid.len);
>>  			WRITEMEM(info.oid.data, info.oid.len);
>> -- 
>> 1.8.4.2
>