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

[Paulo Alcantara <pcacjr@zytor.com>]

On 9/12/2017 8:27 AM, Laszlo Ersek wrote:
> 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>

Ping? :-)

Thanks!
Paulo