[PATCH v1 1/1] UefiCpuPkg: PiSmmCpuDxeSmm: Check buffer size before accessing

["Kun Qin" <kuqin12@gmail.com>]

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3283

Current SMM Save State routine does not check the number of bytes to be
read, when it comse to read IO_INFO, before casting the incoming buffer
to EFI_SMM_SAVE_STATE_IO_INFO. This could potentially cause memory
corruption due to extra bytes are written out of buffer boundary.

This change adds a width check before copying IoInfo into output buffer.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>

Signed-off-by: Kun Qin <kuqin12@gmail.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v2:
    - Update return code description [Laszlo]

 UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c | 9 ++++++++-
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 2 +-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c b/UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c
index 661cc51f361a..fc418c2500a9 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/SmramSaveState.c
@@ -343,7 +343,7 @@ ReadSaveStateRegisterByIndex (
 
   @retval EFI_SUCCESS           The register was read from Save State.
   @retval EFI_NOT_FOUND         The register is not defined for the Save State of Processor.
-  @retval EFI_INVALID_PARAMETER  This or Buffer is NULL.
+  @retval EFI_INVALID_PARAMETER Buffer is NULL, or Width does not meet requirement per Register type.
 
 **/
 EFI_STATUS
@@ -418,6 +418,13 @@ ReadSaveStateRegister (
       return EFI_NOT_FOUND;
     }
 
+    //
+    // Make sure the incoming buffer is large enough to hold IoInfo before accessing
+    //
+    if (Width < sizeof (EFI_SMM_SAVE_STATE_IO_INFO)) {
+      return EFI_INVALID_PARAMETER;
+    }
+
     //
     // Zero the IoInfo structure that will be returned in Buffer
     //
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
index b8aa9e1769d3..2248a8c5ee66 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
@@ -337,7 +337,7 @@ This function supports reading a CPU Save State register in SMBase relocation ha
 
 @retval EFI_SUCCESS           The register was read from Save State.
 @retval EFI_NOT_FOUND         The register is not defined for the Save State of Processor.
-@retval EFI_INVALID_PARAMETER  This or Buffer is NULL.
+@retval EFI_INVALID_PARAMETER Buffer is NULL, or Width does not meet requirement per Register type.
 
 **/
 EFI_STATUS
-- 
2.31.0.windows.1