Re: [PATCH 20/21] xenvif: Check the statistic name in frontend

[Owen Smith <owen.smith@xxxxxxxxxx>]

This change isnt strictly necessary - the only callers of 
__FrontendQueryStatistic
are the debug callback, which loops over all values of XENVIF_VIF_STATISTIC_*
and VifQueryStatistic, which already validates the statistic index is within
range (an additional check in the Query path is negligible difference)

I do get warnings where Name is cast to a ULONG
xenvif\src\xenvif\frontend.c(1811): warning C33010: Unchecked lower bound for 
enum Name used as index
xenvif\src\xenvif\frontend.c(1845): warning C33010: Unchecked lower bound for 
enum Name used as index

I'll post a follow up patch to resolve this

Owen

________________________________________
From: win-pv-devel <win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx> on behalf of 
Césaire Mounah <cesaire.mounah@xxxxxxxxxx>
Sent: 12 October 2026 11:23 AM
To: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
Cc: Césaire Mounah
Subject: [PATCH 20/21] xenvif: Check the statistic name in frontend

CodeAnalysis raised a warning on this condition.
Name comes from the VIF interface caller and was only checked with an
ASSERT, so a release build could read past the end of the statistics
array. Return early when the name is out of range.

Signed-off-by: Césaire Mounah <cesaire.mounah@xxxxxxxxxx>
---
 src/xenvif/frontend.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/xenvif/frontend.c b/src/xenvif/frontend.c
index a35ed78..4b4e69f 100644
--- a/src/xenvif/frontend.c
+++ b/src/xenvif/frontend.c
@@ -1800,6 +1800,10 @@ __FrontendQueryStatistic(
     ASSERT3U(Name, <, XENVIF_VIF_STATISTIC_COUNT);

     *Value = 0;
+
+    if (Name >= XENVIF_VIF_STATISTIC_COUNT)
+        return;
+
     for (Index = 0; Index < Frontend->StatisticsCount; Index++) {
         PXENVIF_FRONTEND_STATISTICS Statistics;

--
2.55.0.windows.5



--
Césaire Mounah | Vates Windows Guest Tools Engineer

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