Re: [14/17] nfsd: wrong index used in inner loop

[Tim Gardner <tim.gardner@canonical.com>]

On 03/17/2011 05:00 PM, J. Bruce Fields wrote:
> On Fri, Mar 11, 2011 at 10:21:58PM +0000, Tim Gardner wrote:
>> On 03/11/2011 08:40 PM, Greg KH wrote:
>>> 2.6.32-longterm review patch.  If anyone has any objections, please let us know.
>>>
>>> ------------------
>>>
>>> From: roel<roel.kluin@gmail.com>
>>>
>>> commit 3ec07aa9522e3d5e9d5ede7bef946756e623a0a0 upstream.
>>>
>>> Index i was already used in the outer loop
>>>
>>> Signed-off-by: Roel Kluin<roel.kluin@gmail.com>
>>> Signed-off-by: J. Bruce Fields<bfields@redhat.com>
>>> Signed-off-by: Greg Kroah-Hartman<gregkh@suse.de>
>>>
>>> ---
>>>   fs/nfsd/nfs4xdr.c |    4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> --- a/fs/nfsd/nfs4xdr.c
>>> +++ b/fs/nfsd/nfs4xdr.c
>>> @@ -1114,7 +1114,7 @@ nfsd4_decode_create_session(struct nfsd4
>>>
>>>   	u32 dummy;
>>>   	char *machine_name;
>>> -	int i;
>>> +	int i, j;
>>>   	int nr_secflavs;
>>>
>>>   	READ_BUF(16);
>>> @@ -1187,7 +1187,7 @@ nfsd4_decode_create_session(struct nfsd4
>>>   			READ_BUF(4);
>>>   			READ32(dummy);
>>>   			READ_BUF(dummy * 4);
>>> -			for (i = 0; i<   dummy; ++i)
>>> +			for (j = 0; j<   dummy; ++j)
>>>   				READ32(dummy);
>>>   			break;
>>>   		case RPC_AUTH_GSS:
>>>
>>>
>>> --
>>
>> I agree that fixing the index in this loop is a good thing, but its
>> caused me to look at the result:
>>
>> for (j = 0; j<   dummy; ++j)
>> 	READ32(dummy);
>>
>> It seems to me that this loop might never terminate if the original
>> buffer is maliciously constructed, e.g., 0, 1, 2, 3, ... Is the data
>> in this buffer really that well vetted?
>
> Agreed, the code's still clearly bogus.  In fact, we can just delete
> that loop entirely; I have a patch queued up to send to Linus soon.
>
> (But go ahead and apply this anyway, and then you'll get the followup
> patch when it lands.)
>
> --b.
>

Will do. Thanks for the update.

rtg
-- 
Tim Gardner tim.gardner@canonical.com