[win-pv-devel] [PATCH] Ensure Hash mapping has at least 1 entry when Toeplitz is selected.

[<owen.smith@xxxxxxxxxx>]

From: Owen Smith <owen.smith@xxxxxxxxxx>

Its possible to select Toeplitz hashing without specifiying the hash
map. A divide-by-zero BSOD can occur when a packet is sent before
the hash map is created. Also add an ASSERT to detect potential
divide-by-zeros in checked builds.

Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
---
 src/xenvif/frontend.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/xenvif/frontend.c b/src/xenvif/frontend.c
index f6570e8..0b51fd1 100644
--- a/src/xenvif/frontend.c
+++ b/src/xenvif/frontend.c
@@ -1863,6 +1863,12 @@ __FrontendUpdateHash(
         break;
 
     case XENVIF_PACKET_HASH_ALGORITHM_TOEPLITZ:
+        if (Hash->Size == 0) {
+            // if Algorithm is set without setting a hash map,
+            // we need to ensure the hash map has 1 entry (0)
+            Hash->Size = 1;
+            Hash->Mapping[0] = 0;
+        }
         Size = Hash->Size;
         Mapping = Hash->Mapping;
         Flags = Hash->Flags;
@@ -2151,6 +2157,7 @@ FrontendGetQueue(
         break;
 
     case XENVIF_PACKET_HASH_ALGORITHM_TOEPLITZ:
+        ASSERT3U(Frontend->Hash.Size, != , 0);
         Queue = Frontend->Hash.Mapping[Value % Frontend->Hash.Size];
         break;
 
-- 
2.8.3


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