[PATCH] Check Fragment is non-null

[Owen Smith <owen.smith@xxxxxxxxxx>]

When processing a response, the id value should indicate the index into
the Pending array, of the relevant Fragment. In some situations, its
possible that the Pending array entry has already been NULLed, likely
due to a backend inserted response coinciding with a frontend faked
response. If the Fragment returned from the Pending array is NULL, then
any attempt to access this NULL Fragment will result in a bugcheck.
Skip any responses where the related Pending entry has already been NULLed.

Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
---
 src/xenvif/transmitter.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/xenvif/transmitter.c b/src/xenvif/transmitter.c
index 0f7deb1..58f8575 100644
--- a/src/xenvif/transmitter.c
+++ b/src/xenvif/transmitter.c
@@ -2525,7 +2525,9 @@ TransmitterRingPoll(
             Fragment = Ring->Pending[id];
             Ring->Pending[id] = NULL;
 
-            ASSERT(Fragment != NULL);
+            if (Fragment == NULL)
+                continue;
+
             ASSERT3U(Fragment->Id, ==, id);
 
             switch (Fragment->Type) {
-- 
2.51.2.windows.1