NetworkPkg/SnpDxe: Prevent invalid PCI BAR access

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1563

SnpDxe initializes values for MemoryBarIndex and IoBarIndex to 0 and 1
respectively even if calls to PciIo->GetBarAttributes never return
success.

Later, if the BAR is used to perform IO/Mem reads/writes, a potentially
non-existent BAR index may be accessed. This change initializes the
values
to an invalid BAR index (PCI_MAX_BAR) so the condition can be explicitly
checked to avoid an invalid BAR access.

Cc: Siyuan Fu <siyuan.fu@intel.com>
Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Siyuan Fu <siyuan.fu@intel.com>
Reviewed-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/NetworkPkg/SnpDxe/Snp.c b/NetworkPkg/SnpDxe/Snp.c
index fe022e16ea..69e74132ed 100644
--- a/NetworkPkg/SnpDxe/Snp.c
+++ b/NetworkPkg/SnpDxe/Snp.c
@@ -466,8 +466,8 @@ SimpleNetworkDriverStart (
   // the IO BAR.  Save the index of the BAR into the adapter info structure.

   // for regular 32bit BARs, 0 is memory mapped, 1 is io mapped

   //

-  Snp->MemoryBarIndex = 0;

-  Snp->IoBarIndex     = 1;

+  Snp->MemoryBarIndex = PCI_MAX_BAR;

+  Snp->IoBarIndex     = PCI_MAX_BAR;

   FoundMemoryBar      = FALSE;

   FoundIoBar          = FALSE;

   for (BarIndex = 0; BarIndex < PCI_MAX_BAR; BarIndex++) {