From c188c382afcad1a054541f8b101fa1044e2289cf Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Sun, 2 Jun 2019 19:02:25 +0100
Subject: [PATCH spice-gtk] vmcstream: Fix buffer overflow sending data to task
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The "count" variable is used to store the full length of the
initial buffer set using spice_vmc_input_stream_read_all_async or
spice_vmc_input_stream_read_async.
However on spice_vmc_input_stream_co_data the "buffer" variable is
increased by the amount read into it.
On potential next loop "count" is still used to compute the bytes to
read but now "buffer + count" points past the original buffer.
So we need to take into account the position written in order to
compute the right limit.
Tested with WebDAV.

https://bugzilla.redhat.com/show_bug.cgi?id=1720532

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 src/vmcstream.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/src/vmcstream.c b/src/vmcstream.c
index 0634bce..86c949a 100644
--- a/src/vmcstream.c
+++ b/src/vmcstream.c
@@ -142,17 +142,16 @@ spice_vmc_input_stream_co_data(SpiceVmcInputStream *self,
 
         g_return_if_fail(self->task != NULL);
 
-        gsize min = MIN(self->count, size);
-        memcpy(self->buffer, data, min);
+        gsize min = MIN(self->count - self->pos, size);
+        memcpy(self->buffer + self->pos, data, min);
 
         size -= min;
         data += min;
 
-        SPICE_DEBUG("spicevmc co_data complete: %" G_GSIZE_FORMAT
-                    "/%" G_GSIZE_FORMAT, min, self->count);
-
         self->pos += min;
-        self->buffer += min;
+
+        SPICE_DEBUG("spicevmc co_data complete: %" G_GSIZE_FORMAT
+                    "/%" G_GSIZE_FORMAT, self->pos, self->count);
 
         if (self->all && min > 0 && self->pos != self->count)
             continue;
-- 
2.22.0.rc2.384.g1a9a72ea1d