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

["J. Bruce Fields" <bfields@fieldses.org>]

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.

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

--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