Re: [PATCH v3] libselinux: correct error path to always try text

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On Fri, Sep 16, 2016 at 8:04 AM, William Roberts
<bill.c.roberts@xxxxxxxxx> wrote:
> On Fri, Sep 16, 2016 at 8:00 AM, Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:
>> On 09/16/2016 10:44 AM, William Roberts wrote:
>>> On Fri, Sep 16, 2016 at 7:41 AM, William Roberts
>>> <bill.c.roberts@xxxxxxxxx> wrote:
>>>> On Fri, Sep 16, 2016 at 7:38 AM, Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:
>>>>> On 09/16/2016 10:30 AM, Stephen Smalley wrote:
>>>>>> On 09/15/2016 07:13 PM, william.c.roberts@xxxxxxxxx wrote:
>>>>>>> From: William Roberts <william.c.roberts@xxxxxxxxx>
>>>>>>>
>>>>>>> patch 5e15a52aaa cleans up the process_file() but introduced
>>>>>>> a bug. If the binary file cannot be opened, always attempt
>>>>>>> to fall back to the textual file, this was not occurring.
>>>>>>>
>>>>>>> The logic should be:
>>>>>>> 1. Open the newest file based on base path + suffix vs
>>>>>>>    base_path + suffix + ".bin".
>>>>>>> 2. If anything fails, attempt base_path + suffix.
>>>>>>>
>>>>>>> In the case that the file_contexts was the newest file and
>>>>>>> used for processing fails, it will attempt the same failure
>>>>>>> recovery, which will fail. It was decided to keep it this
>>>>>>> was for simplicity.
>>>>>>
>>>>>> I don't like the approach.  What we want is:
>>>>>> - if .bin file exists and is not older, try to load it,
>>>>>> - if any of the above fails (i.e. .bin file does not exist, is older, or
>>>>>> cannot be loaded for any reason), then load the text file.
>>>>>>
>>>>>> We shouldn't try loading the text file twice.
>>>>>>
>>>>>> Also, attached is checkpatch output for your patch.  Please fix.
>>>>>
>>>>> Also, there is a further wrinkle: Android passes in file_contexts.bin as
>>>>> the SELABEL_OPT_PATH, so that is the base path.  Under the old logic
>>>>> (before your original clean up patch), we would open that file, detect
>>>>> that it is binary, and then load it.  Under the current logic, we'll
>>>>> open file_contexts.bin, then try to open file_contexts.bin.bin (which
>>>>> will fail), and then use the first one.
>>>>
>>>> Not true, I don't try to open it, I try to stat it.
>>>
>>> My code never assumes file suffix == type
>>>
>>>>
>>>>>
>>>>> Wondering if we just need to revert.
>>>>
>>>> If you want to revert I have no problem with that, but I provided IMO
>>>> a valid fix.
>>>> Since I won't likely have a next version patch out till after you go
>>>> home today, I
>>>> would support reverting.
>>
>> Unfortunately it is now entangled with Janis' patch.  Let's do this: fix
>> the coding style issues I sent to you from checkpatch, and we'll take
>> this one.  Then we'll look to avoid the extraneous load in a subsequent
>> patch.
>
> Fine by me, i'm running to an appointment, I wont have that patch out to
> probably 3-4pm your time.

BTW did you not get v3 of this patch?

I also thought about the additional load attempt even on "textual"
files, and I would
argue we keep it with a slight modification. The boolean flag passed
to open_file should really
by called, choose oldest file and invert the time comparison logic.
This way, if one file
is corrupted, we always attempt to load the other file. Also, all of
this code is agnostic to
file extension determining content type. This code, with that change
would work in the
case file_contexts is newer and corrupted, it will try to fall back on
binary file.


>
> --
> Respectfully,
>
> William C Roberts



-- 
Respectfully,

William C Roberts
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