[U-Boot] [PATCH] fat: handle paths that include ../

[Stephen Warren <swarren@wwwdotorg.org>]

On 09/10/2015 03:26 PM, Tom Rini wrote:
> On Thu, Sep 10, 2015 at 10:22:35AM -0700, Stephen Warren wrote:
>> On 07/28/2015 08:55 PM, Stephen Warren wrote:
>>> The FAT code contains a special case to parse the root
>>> directory. This is needed since the root directory
>>> location/layout on disk is special cased for FAT12/16. In
>>> particular, the location and size of the FAT12/16 root
>>> directory is hard-coded and contiguous, whereas all FAT12/16
>>> non-root directories, and all FAT32 directories, are stored in
>>> a non-contiguous fashion, with the layout represented by a
>>> linked-list of clusters in the FAT.
>>> 
>>> If a file path contains ../ (for example
>>> /extlinux/../bcm2835-rpi-cm.dtb), it is possible to need to
>>> parse the root directory for the first element in the path
>>> (requiring application of the special case), then a sub- 
>>> directory (in the general way), then re-parse the root
>>> directory (again requiring the special case). However, the
>>> current code in U-Boot only applies the special case for the
>>> very first path element, and never for any later path element.
>>> When reparsing the root directory without applying the special
>>> case, any file in a sector (or cluster?) other than the first
>>> sector/cluster of the root directory will not be found.
>>> 
>>> This change modifies the non-root-dir-parsing loop of
>>> do_fat_read_at() to detect if it's walked back to the root
>>> directory, and if so, jumps back to the special case code that
>>> handles parsing of the root directory.
>> 
>> Is this change slated for v2015.10, or is the plan to leave this
>> issue in place until the FAT implementation replacement is
>> accepted for the release after that?
> 
> I believe I shall grab this.  Did you see the email from Lukasz
> saying the new FAT didn't pass the DFU test suite?

Yes. I'll try testing that when I get back from travel.