Merry Christmas!

On 12/25/2013 6:36 AM, Nicolas Iooss wrote:
> 2013/12/23 Daniel J Walsh wrote:
>> On 12/21/2013 09:27 AM, Nicolas Iooss wrote:
>>> My first message was not so clear. The check in
>>> libselinux/src/lsetfilecon.c line 35 [1] doesn't work because
>>> selinux_trans_to_raw_context(context, &rcontext) returns 0 and sets
>>> rcontext to NULL. This is why I'm asking to change the return value to
>>> something else if you want "cp -a" working. This fix is not to introduce a
>>> new feature but to fix an existing one.
>>>
>>> Nicolas
>>>
>> How about if we add a check on lsetfilecon_raw?  Changing the behaviour on
>> selinux_trans_to_raw_context might cause other problems.
> I agree. I've found
> http://selinuxproject.org/page/LibselinuxAPISummary which says
> precisely for selinux_trans_to_raw_context: "If passed NULL, sets the
> returned context to NULL and returns 0." As this feature is
> documented, callers may rely on it and changing this behavior is
> likely to break things.
>
> Moreover setfilecon_raw and fsetfilecon_raw have the same NULL-pointer
> dereference issue. Do these functions need a patch too?
>
> By the way, other callers of selinux_trans_to_raw_context may also
> share this bug: avc_context_to_sid, security_canonicalize_context,
> security_check_context, etc. Is doing a segmentation fault the
> expected way to tell the caller it used a NULL pointer and should have
> manually checked every parameter before calling any libselinux
> function?
>
> Thanks and merry Christmas!
>
> Nicolas
>
>>
>> diff --git a/libselinux/src/lsetfilecon.c b/libselinux/src/lsetfilecon.c
>> index 461e3f7..af3775e 100644
>> - --- a/libselinux/src/lsetfilecon.c
>> +++ b/libselinux/src/lsetfilecon.c
>> @@ -9,6 +9,10 @@
>>
>>   int lsetfilecon_raw(const char *path, const security_context_t context)
>>   {
>> +       if (! context) {
>> +               errno=EINVAL;
>> +               return -1;
>> +       }
>>          return lsetxattr(path, XATTR_NAME_SELINUX, context, strlen(context) + 1
>>                           0);
>>   }
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