Re: [PATCH] MdePkg-BaseLib: Fix PathCleanUpDirectories() error involving "\..\.."

[<Jim.Dailey@dell.com>]

>-----Original Message-----
>From: Ni, Ruiyu [mailto:ruiyu.ni@Intel.com] 
>Sent: Monday, October 8, 2018 2:00 AM
>To: Dailey, Jim; edk2-devel@lists.01.org
>Cc: michael.d.kinney@intel.com; liming.gao@intel.com
>Subject: Re: [edk2] [PATCH] MdePkg-BaseLib: Fix PathCleanUpDirectories() error involving "\..\.."
>
>
>On 10/4/2018 11:03 PM, Jim.Dailey@dell.com wrote:
>> MdePkg-BaseLib: Fix PathCleanUpDirectories() error involving "\..\.."
>> 
>> The loop that removes "xxxx\..\" errs when multiple "\.." sequences are
>> in the path.  Before this change the code would modify a path like
>> "FS0:\efi\tools\..\.." to "FS0:\efi\\.." and then to "FS0:\efi\", but
>> the correct path is "FS0:\".
>> 
>> You can test the effect of this change in the shell by setting the
>> current directory to something like FS0:\efi\boot and then executing
>> the command "ls ..\..".  Before the change you will see the files in
>> the FS0:\efi directory; after the change, you will see the files in
>> the root directory of FS0:.
>> 
>> Contributed-under: TianoCore Contribution Agreement 1.1
>> Signed-off-by: Jim Dailey <jim_dailey@dell.com>
>> ---
>>   MdePkg/Library/BaseLib/FilePaths.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>> 
>> diff --git a/MdePkg/Library/BaseLib/FilePaths.c b/MdePkg/Library/BaseLib/FilePaths.c
>> index d6f3758ecb..5d3de01894 100644
>> --- a/MdePkg/Library/BaseLib/FilePaths.c
>> +++ b/MdePkg/Library/BaseLib/FilePaths.c
>> @@ -2,6 +2,7 @@
>>     Defines file-path manipulation functions.
>>   
>>     Copyright (c) 2011 - 2017, Intel Corporation. All rights reserved.<BR>
>> +  Copyright (c) 2018, Dell Technologies. All rights reserved.<BR>
>>     This program and the accompanying materials
>>     are licensed and made available under the terms and conditions of the BSD License
>>     which accompanies this distribution.  The full text of the license may be found at
>> @@ -103,7 +104,9 @@ PathCleanUpDirectories(
>>           ) {
>>       *(TempString + 1) = CHAR_NULL;
>>       PathRemoveLastItem(Path);
>> -    CopyMem (Path + StrLen (Path), TempString + 3, StrSize (TempString + 3));
>> +    if (*(TempString + 3)) {
>> +      CopyMem (Path + StrLen (Path), TempString + 4, StrSize (TempString + 4));
>> +    }
>>     }
>>   
>>     //
>> 
>Jim,
>Are you fixing a corner case bug introduced by following commit:
>
> > SHA-1: bb99e3282c9e69fbd6365d117c58d15589e34c5d
>* MdePkg/BaseLib: Fix PathCleanUpDirectories to correctly handle "\.\"
>
> > The old code incorrectly cleans path like "fs0:\abc\.\.." to
> > "fs0:\abc", instead of "fs0:\"
>
> > The patch fixes this bug.

Honestly, because of the scope of bb99e328, I cannot say for sure, but
my inclination is to answer "No."

The current fix is strictly related to handling paths that include two
or more references to the previous directory, whether or not one of them
abuts a reference to the current directory (as in the bb99e328 fix).

Regards,
Jim