Re: [PATCH 02/23] gss_krb5: Added and improved code comments

Chuck Lever
2010-03-17T17:11:27Z

On 03/17/2010 01:02 PM, steved@redhat.com wrote:
> From: Kevin Coffman<kwc@citi.umich.edu>
>
> Signed-off-by: Steve Dickson<steved@redhat.com>
> ---
> net/sunrpc/auth_gss/auth_gss.c | 12 +++++++++---
> net/sunrpc/auth_gss/gss_mech_switch.c | 14 ++++++++++++++
> net/sunrpc/auth_gss/svcauth_gss.c | 15 +++++++++++++++
> 3 files changed, 38 insertions(+), 3 deletions(-)
>
> diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
> index 7c50ea6..a268368 100644
> --- a/net/sunrpc/auth_gss/auth_gss.c
> +++ b/net/sunrpc/auth_gss/auth_gss.c
> @@ -1317,15 +1317,21 @@ gss_wrap_req_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
> inpages = snd_buf->pages + first;
> snd_buf->pages = rqstp->rq_enc_pages;
> snd_buf->page_base -= first<< PAGE_CACHE_SHIFT;
> - /* Give the tail its own page, in case we need extra space in the
> - * head when wrapping: */
> + /*
> + * Give the tail its own page, in case we need extra space in the
> + * head when wrapping:
> + *
> + * call_allocate() allocates twice the slack space required
> + * by the authentication flavor to rq_callsize.
> + * For GSS, slack is GSS_CRED_SLACK.
> + */
> if (snd_buf->page_len || snd_buf->tail[0].iov_len) {
> tmp = page_address(rqstp->rq_enc_pages[rqstp->rq_enc_pages_num - 1]);
> memcpy(tmp, snd_buf->tail[0].iov_base, snd_buf->tail[0].iov_len);
> snd_buf->tail[0].iov_base = tmp;
> }
> maj_stat = gss_wrap(ctx->gc_gss_ctx, offset, snd_buf, inpages);
> - /* RPC_SLACK_SPACE should prevent this ever happening: */
> + /* slack space should prevent this ever happening: */
> BUG_ON(snd_buf->len> snd_buf->buflen);
> status = -EIO;
> /* We're assuming that when GSS_S_CONTEXT_EXPIRED, the encryption was
> diff --git a/net/sunrpc/auth_gss/gss_mech_switch.c b/net/sunrpc/auth_gss/gss_mech_switch.c
> index 76e4c6f..28a84ef 100644
> --- a/net/sunrpc/auth_gss/gss_mech_switch.c
> +++ b/net/sunrpc/auth_gss/gss_mech_switch.c
> @@ -285,6 +285,20 @@ gss_verify_mic(struct gss_ctx *context_handle,
> mic_token);
> }
>
> +/*
> + * This function is called from both the client and server code.
> + * Each makes guarantees about how much "slack" space is available
> + * for the underlying function in "buf"'s head and tail while
> + * performing the wrap.
> + *
> + * The client and server code allocate RPC_MAX_AUTH_SIZE extra
> + * space in both the head and tail which is available for use by
> + * the wrap function.
> + *
> + * Underlying functions should verify they do not use more than
> + * RPC_MAX_AUTH_SIZE of extra space in either the head or tail
> + * when performing the wrap.
> + */

gss_wrap is globally visible, so this should be a doxygen style comment,
yes?

> u32
> gss_wrap(struct gss_ctx *ctx_id,
> int offset,
> diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
> index e34bc53..4eec8ba 100644
> --- a/net/sunrpc/auth_gss/svcauth_gss.c
> +++ b/net/sunrpc/auth_gss/svcauth_gss.c
> @@ -1314,6 +1314,14 @@ svcauth_gss_wrap_resp_priv(struct svc_rqst *rqstp)
> inpages = resbuf->pages;
> /* XXX: Would be better to write some xdr helper functions for
> * nfs{2,3,4}xdr.c that place the data right, instead of copying: */
> +
> + /*
> + * If there is currently tail data, make sure there is
> + * room for the head, tail, and 2 * RPC_MAX_AUTH_SIZE in
> + * the page, and move the current tail data such that
> + * there is RPC_MAX_AUTH_SIZE slack space available in
> + * both the head and tail.
> + */
> if (resbuf->tail[0].iov_base) {
> BUG_ON(resbuf->tail[0].iov_base>= resbuf->head[0].iov_base
> + PAGE_SIZE);
> @@ -1326,6 +1334,13 @@ svcauth_gss_wrap_resp_priv(struct svc_rqst *rqstp)
> resbuf->tail[0].iov_len);
> resbuf->tail[0].iov_base += RPC_MAX_AUTH_SIZE;
> }
> + /*
> + * If there is no current tail data, make sure there is
> + * room for the head data, and 2 * RPC_MAX_AUTH_SIZE in the
> + * allotted page, and set up tail information such that there
> + * is RPC_MAX_AUTH_SIZE slack space available in both the
> + * head and tail.
> + */
> if (resbuf->tail[0].iov_base == NULL) {
> if (resbuf->head[0].iov_len + 2*RPC_MAX_AUTH_SIZE> PAGE_SIZE)
> return -ENOMEM;

--
chuck[dot]lever[at]oracle[dot]com