Re: [PATCH] MdeModulePkg/UdfDxe: Fix NULL pointer dereference

[Laszlo Ersek <lersek@redhat.com>]

On 09/12/17 03:30, Paulo Alcantara wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=704
> 
> For root directory, the FID (File Identifier Descriptor) pointer is
> accessible through PRIVATE_UDF_FILE_DATA.Root, whereas non-root
> directory and regular files, their FIDs are accessible through
> PRIVATE_UDF_FILE_DATA.File.
> 
> In UdfSetPosition(), the FID was retrieved through
> PRIVATE_UDF_FILE_DATA.File, hence when calling it with a root directory,
> PRIVATE_UDF_FILE_DATA.File.FileIdentifierDescriptor would be NULL and
> then dereferenced.
> 
> This patch fixes the NULL pointer dereference by calling _FILE() to
> transparently return the correct UDF_FILE_INFO * which points to a valid
> FID descriptor of a specific file.
> 
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Steven Shi <steven.shi@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Reported-by: Steven Shi <steven.shi@intel.com>
> Signed-off-by: Paulo Alcantara <pcacjr@zytor.com>
> ---
>  MdeModulePkg/Universal/Disk/UdfDxe/File.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/MdeModulePkg/Universal/Disk/UdfDxe/File.c b/MdeModulePkg/Universal/Disk/UdfDxe/File.c
> index 8b9339567f..a1eb2196df 100644
> --- a/MdeModulePkg/Universal/Disk/UdfDxe/File.c
> +++ b/MdeModulePkg/Universal/Disk/UdfDxe/File.c
> @@ -690,7 +690,8 @@ UdfSetPosition (
>  
>    PrivFileData = PRIVATE_UDF_FILE_DATA_FROM_THIS (This);
>  
> -  FileIdentifierDesc = PrivFileData->File.FileIdentifierDesc;
> +  FileIdentifierDesc = _FILE (PrivFileData)->FileIdentifierDesc;
> +  ASSERT (FileIdentifierDesc != NULL);
>    if (IS_FID_DIRECTORY_FILE (FileIdentifierDesc)) {
>      //
>      // If the file handle is a directory, the _only_ position that may be set is
> 

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

Thanks!
Laszlo