[Xen-changelog] [xen staging] libxl_qmp: Move the buffer realloc to the same scope level as read

[patchbot@xxxxxxx]

commit 75ac495dc9d6aa3d6240bfab1adbdc0d0f8bc403
Author:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
AuthorDate: Fri Jul 27 15:05:47 2018 +0100
Commit:     Wei Liu <wei.liu2@xxxxxxxxxx>
CommitDate: Mon Jul 30 14:46:32 2018 +0100

    libxl_qmp: Move the buffer realloc to the same scope level as read
    
    In qmp_next(), the inner loop should only try to parse messages from
    QMP, if there is more than one.
    
    The handling of the receive buffer ('incomplete'), should be done at the
    same scope level as read(). It doesn't need to be handle more that once
    after a read.
    
    Before this patch, when on message what handled, the inner loop would
    restart by adding the 'buffer' into 'incomplete' (after reallocation).
    Since 'rd' was not reset, the buffer would be strcat a second time.
    After that, the stream from the QMP server would have syntax error, and
    the parsor would throw errors.
    
    This is unlikely to happen as the receive buffer is very large. And
    receiving two messages in a row is unlikely. In the current case, this
    could be an event and a response to a command.
    
    Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
    Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 tools/libxl/libxl_qmp.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index 27227802e4..5b608f47e5 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -530,23 +530,24 @@ static int qmp_next(libxl__gc *gc, libxl__qmp_handler 
*qmp)
 
         DEBUG_REPORT_RECEIVED(qmp->domid, qmp->buffer, (int)rd);
 
+        if (incomplete) {
+            size_t current_pos = s - incomplete;
+            incomplete = libxl__realloc(gc, incomplete,
+                                        incomplete_size + rd + 1);
+            strncat(incomplete + incomplete_size, qmp->buffer, rd);
+            s = incomplete + current_pos;
+            incomplete_size += rd;
+            s_end = incomplete + incomplete_size;
+        } else {
+            incomplete = libxl__strndup(gc, qmp->buffer, rd);
+            incomplete_size = rd;
+            s = incomplete;
+            s_end = s + rd;
+            rd = 0;
+        }
+
         do {
             char *end = NULL;
-            if (incomplete) {
-                size_t current_pos = s - incomplete;
-                incomplete = libxl__realloc(gc, incomplete,
-                                            incomplete_size + rd + 1);
-                strncat(incomplete + incomplete_size, qmp->buffer, rd);
-                s = incomplete + current_pos;
-                incomplete_size += rd;
-                s_end = incomplete + incomplete_size;
-            } else {
-                incomplete = libxl__strndup(gc, qmp->buffer, rd);
-                incomplete_size = rd;
-                s = incomplete;
-                s_end = s + rd;
-                rd = 0;
-            }
 
             end = strstr(s, "\r\n");
             if (end) {
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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