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

steved
2010-03-17T17:03:11Z

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.
+ */
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;
--
1.6.6.1