Re: [PATCH] rpc: Correct the wrong payload size checking

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On 14/10/13 21:26, Daniel P. Berrange wrote:
On Mon, Oct 14, 2013 at 03:22:27PM +0800, Osier Yang wrote:
<...>
/* Size of message length field. Not counted in VIR_NET_MESSAGE_MAX
  * and VIR_NET_MESSAGE_INITIAL.
  */
const VIR_NET_MESSAGE_LEN_MAX = 4;
</...>

However, msg->bufferLength includes the length word. The wrong checking
was introduced by commit e914dcfd.

* src/rpc/virnetmessage.c:
   - Correct the checking in virNetMessageEncodePayloadRaw
   - Use a new variable to track the new payload length in
     virNetMessageEncodePayloadRaw
---
  src/rpc/virnetmessage.c | 19 +++++++++++++------
  1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/rpc/virnetmessage.c b/src/rpc/virnetmessage.c
index 8f4e4bc..4c60424 100644
--- a/src/rpc/virnetmessage.c
+++ b/src/rpc/virnetmessage.c
@@ -346,15 +346,17 @@ int virNetMessageEncodePayload(virNetMessagePtr msg,
/* Try to encode the payload. If the buffer is too small increase it. */
      while (!(*filter)(&xdr, data)) {
-        if ((msg->bufferLength - VIR_NET_MESSAGE_LEN_MAX) * 4 > VIR_NET_MESSAGE_MAX) {
+        unsigned int newlen = (msg->bufferLength - VIR_NET_MESSAGE_LEN_MAX) * 4 +
+            VIR_NET_MESSAGE_LEN_MAX;
+
+        if (newlen > VIR_NET_MESSAGE_MAX + VIR_NET_MESSAGE_LEN_MAX) {
You've not actually changed the logic here at all - you've just
added VIR_NET_MESSAGE_LEN_MAX to both sides of the '>'. So this
change is a no-op. Please drop it.

Yes, the logic is not changed, but I wanted to calculate the new buffer length once instead of twice, and it's more readable for the code. So I'd like keep it.



              virReportError(VIR_ERR_RPC, "%s", _("Unable to encode message payload"));
              goto error;
          }
xdr_destroy(&xdr); - msg->bufferLength = (msg->bufferLength - VIR_NET_MESSAGE_LEN_MAX) * 4 +
-            VIR_NET_MESSAGE_LEN_MAX;
+        msg->bufferLength = newlen;
Again, nothing changed. Drop this.

if (VIR_REALLOC_N(msg->buffer, msg->bufferLength) < 0)
              goto error;
@@ -426,10 +428,15 @@ int virNetMessageEncodePayloadRaw(virNetMessagePtr msg,
/* If the message buffer is too small for the payload increase it accordingly. */
      if ((msg->bufferLength - msg->bufferOffset) < len) {
-        if ((msg->bufferOffset + len) > VIR_NET_MESSAGE_MAX) {
+        if ((msg->bufferOffset + len) >
+            VIR_NET_MESSAGE_MAX + VIR_NET_MESSAGE_LEN_MAX) {
Bracket both sides of the '>' for clarity, not just the left-hand-side.


So except this, Can I get an ACK?


diff --git a/src/rpc/virnetmessage.c b/src/rpc/virnetmessage.c
index 4c60424..79a50f6 100644
--- a/src/rpc/virnetmessage.c
+++ b/src/rpc/virnetmessage.c
@@ -429,7 +429,7 @@ int virNetMessageEncodePayloadRaw(virNetMessagePtr msg,
     /* If the message buffer is too small for the payload increase it accordingly. */
     if ((msg->bufferLength - msg->bufferOffset) < len) {
         if ((msg->bufferOffset + len) >
-            VIR_NET_MESSAGE_MAX + VIR_NET_MESSAGE_LEN_MAX) {
+            (VIR_NET_MESSAGE_MAX + VIR_NET_MESSAGE_LEN_MAX)) {
             virReportError(VIR_ERR_RPC,
                            _("Stream data too long to send "
                              "(%zu bytes needed, %zu bytes available)"),
--
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