Re: [edk2-devel] [PATCH v3 4/4] StandaloneMmPkg: Disallow unregister MMI handler in other MMI handler

["Laszlo Ersek" <lersek@redhat.com>]

On 3/1/24 04:01, Zhiguang Liu wrote:
> In last patch, we add code support to unregister MMI handler inside
> itself. However, the code doesn't support unregister MMI handler
> insider other MMI handler. While this is not a must-have usage.
> So add check to disallow unregister MMI handler in other MMI handler.
> 
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> Cc: Jiaxin Wu <jiaxin.wu@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Sami Mujawar <sami.mujawar@arm.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
> ---
>  StandaloneMmPkg/Core/Mmi.c | 32 +++++++++++++++++++++++---------
>  1 file changed, 23 insertions(+), 9 deletions(-)
> 
> diff --git a/StandaloneMmPkg/Core/Mmi.c b/StandaloneMmPkg/Core/Mmi.c
> index c1a1d76e85..9e52072bf7 100644
> --- a/StandaloneMmPkg/Core/Mmi.c
> +++ b/StandaloneMmPkg/Core/Mmi.c
> @@ -36,8 +36,9 @@ typedef struct {
>    MMI_ENTRY                     *MmiEntry;
>  } MMI_HANDLER;
>  
> -LIST_ENTRY  mRootMmiHandlerList = INITIALIZE_LIST_HEAD_VARIABLE (mRootMmiHandlerList);
> -LIST_ENTRY  mMmiEntryList       = INITIALIZE_LIST_HEAD_VARIABLE (mMmiEntryList);
> +LIST_ENTRY   mRootMmiHandlerList = INITIALIZE_LIST_HEAD_VARIABLE (mRootMmiHandlerList);
> +LIST_ENTRY   mMmiEntryList       = INITIALIZE_LIST_HEAD_VARIABLE (mMmiEntryList);
> +MMI_HANDLER  *mCurrentMmiHandler = NULL;
>  
>  /**
>    Finds the MMI entry for the requested handler type.
> @@ -161,13 +162,19 @@ MmiManage (
>      // get next node before handler is executed, since LIST_ENTRY that
>      // Link points to may be freed if unregister MMI handler.
>      //
> -    Link   = Link->ForwardLink;
> -    Status = MmiHandler->Handler (
> -                           (EFI_HANDLE)MmiHandler,
> -                           Context,
> -                           CommBuffer,
> -                           CommBufferSize
> -                           );
> +    Link = Link->ForwardLink;
> +    //
> +    // Assign gCurrentMmiHandle before calling the MMI handler and
> +    // set to NULL when it returns.
> +    //
> +    mCurrentMmiHandler = MmiHandler;
> +    Status             = MmiHandler->Handler (
> +                                       (EFI_HANDLE)MmiHandler,
> +                                       Context,
> +                                       CommBuffer,
> +                                       CommBufferSize
> +                                       );
> +    mCurrentMmiHandler = NULL;
>  
>      switch (Status) {
>        case EFI_INTERRUPT_PENDING:
> @@ -314,6 +321,13 @@ MmiHandlerUnRegister (
>      return EFI_INVALID_PARAMETER;
>    }
>  
> +  //
> +  // Do not allow to unregister MMI Handler inside other MMI Handler
> +  //
> +  if ((mCurrentMmiHandler != NULL) && (mCurrentMmiHandler != MmiHandler)) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
>    MmiEntry = MmiHandler->MmiEntry;
>  
>    RemoveEntryList (&MmiHandler->Link);

Reviewed-by: Laszlo Ersek <lersek@redhat.com>



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