From 62016c1e898434a0326f658912b1e7e0a9c5575e Mon Sep 17 00:00:00 2001 From: Star Zeng Date: Fri, 9 Dec 2016 14:47:03 +0800 Subject: [PATCH] MdeModulePkg VariableSmm: Do not need check CommBufferSize buffer Current code in SmmVariableHandler() checks CommBufferSize buffer to make sure it points to outside SMRAM in "case SMM_VARIABLE_FUNCTION_GET_STATISTICS". But after eaae7b33b1cf6b9f21db1636f219c2b6a8d88afd, CommBufferSize buffer points to SMRAM that was used by SMM core to cache CommSize from SmmCommunication protocol, then the check will fail definitely and GET_STATISTICS feature breaks. In fact, do not need check CommBufferSize buffer at all even before eaae7b33b1cf6b9f21db1636f219c2b6a8d88afd. Before eaae7b33b1cf6b9f21db1636f219c2b6a8d88afd, CommBufferSize buffer pointed to gSmmCorePrivate->BufferSize that is outside SMRAM, the check will success definitely; after eaae7b33b1cf6b9f21db1636f219c2b6a8d88afd, CommBufferSize buffer points to local variable BufferSize (in SMRAM) in SmmEntryPoint(), the check is not needed definitely. The patch is to remove the check. Cc: Jiewen Yao Cc: Jeff Fan Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Star Zeng Reviewed-by: Jiewen Yao --- MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c b/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c index eafb53322e..c714916019 100644 --- a/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c +++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c @@ -695,11 +695,10 @@ SmmVariableHandler ( // It is covered by previous CommBuffer check // - if (!SmmIsBufferOutsideSmmValid ((EFI_PHYSICAL_ADDRESS)(UINTN)CommBufferSize, sizeof(UINTN))) { - DEBUG ((EFI_D_ERROR, "GetStatistics: SMM communication buffer in SMRAM!\n")); - Status = EFI_ACCESS_DENIED; - goto EXIT; - } + // + // Do not need to check CommBufferSize buffer as it should point to SMRAM + // that was used by SMM core to cache CommSize from SmmCommunication protocol. + // Status = SmmVariableGetStatistics (VariableInfo, &InfoSize); *CommBufferSize = InfoSize + SMM_VARIABLE_COMMUNICATE_HEADER_SIZE; -- 2.39.2