gss_krb5: Added and improved code comments

Signed-off-by: Steve Dickson <steved@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index 75602ece58eb73f0e984c2cdb41eb880fc4f4924..d64a58b8ed33680ea34078051a9ccd44039562d3 100644 (file)
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1316,15 +1316,21 @@ 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 76e4c6f4ac3c1ad8f58f1f7a92bf7781d05b18a3..28a84ef41d13b520f668c67b94818a47a26d9492 100644 (file)
--- 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.
+ */
 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 b81e790ef9f4197477c6eef889e1f315afd2c8a1..1d9ac4ac818a76c0e70cb02fba277ee1daa02fda 100644 (file)
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -1315,6 +1315,14 @@ 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);
@@ -1327,6 +1335,13 @@ 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;