RFR: 8049695: nsk/jdb/options/connect/connect003 fails with "Launched jdb could not attach to debuggee during 300000 milliseconds"

[Chris Plummer]

Hi Alex,

I don't think prefix -> basename is what David had in mind. Those 
basically mean the same thing. The buffer is being used for the full 
name, which is why neither is really appropriate. So maybe just call it 
fullname, or even just name. createConnection() has a similar prefix 
reference that should be fixed.

thanks,

Chris

On 3/14/18 12:43 PM, Alex Menkov wrote:
>
> Updated fix:
> http://cr.openjdk.java.net/~amenkov/shmem_long_name/webrev_open.02/
>
> The changes:
> - createTransport function is fixed;
> - "prefix" variable is renamed to "baseName".
>
> --alex
>
> On 03/14/2018 09:45, Alex Menkov wrote:
>> Hi David,
>>
>>
>> On 03/13/2018 17:46, David Holmes wrote:
>>> Hi Alex,
>>>
>>> On 14/03/2018 9:14 AM, Alex Menkov wrote:
>>>> Hi all,
>>>>
>>>> Please review a small fix for
>>>> https://bugs.openjdk.java.net/browse/JDK-8049695
>>>> webrev: 
>>>> http://cr.openjdk.java.net/~amenkov/shmem_long_name/webrev_open/
>>>>
>>>> Root cause of the issue is jbd hungs as a result of the buffer 
>>>> overflow.
>>>>
>>>> In the beginning of the shmemBase.c:
>>>>
>>>> #define MAX_IPC_PREFIX 50   /* user-specified or generated name for */
>>>>                              /* shared memory seg and prefix for 
>>>> other IPC */
>>>> #define MAX_IPC_SUFFIX 25   /* suffix to shmem name for other IPC 
>>>> names */
>>>> #define MAX_IPC_NAME   (MAX_IPC_PREFIX + MAX_IPC_SUFFIX)
>>>>
>>>> buffer (char prefix[]) in function createStream is used to generate 
>>>> base name for mutex/events, so MAX_IPC_PREFIX is not big enough.
>>>
>>> Good catch! But overall this code seems to be missing bounds checks 
>>> everywhere. You made the "prefix" (poor name?) buffer bigger 
>>> (MAX_IPC_NAME) but do we know the incoming name plus the appended 
>>> descriptive string will fit in it?
>>
>> Yes, the possible values can be added to the shmem name (which is 
>> restricted by 49 chars):
>> ".mutex"
>> ".hasData"
>> ".hasSpace"
>> ".accept"
>> ".attach"
>> ".<pid>" (pid is 64bit value, max len IIRC is 19 symbols)
>> So extra MAX_IPC_SUFFIX (25 symbols) is enough
>>
>>> Looking at createTransport for example, it also has:
>>>
>>> char prefix[MAX_IPC_PREFIX];
>>>
>>> and it produces an error if
>>>
>>> strlen(address) >= MAX_IPC_PREFIX
>>>
>>> but otherwise copies it across:
>>>
>>> strcpy(transport->name, address);
>>>
>>> and then later does:
>>>
>>>   sprintf(prefix, "%s.mutex", transport->name);
>>>
>>> so we may have overflowed again by adding ".mutex"! The same goes 
>>> for the subsequent sprintf's.
>>
>> Thank you for the catch!
>> I looked the file for other similar issues, but somehow overlokked 
>> this case.
>> Will fix it.
>> Also will change confusing "prefix" name to "base_name".
>>
>> --alex
>>
>>>
>>> So I think there is more work to do to ensure this code is immune 
>>> from buffer overflows.
>>>
>>> Thanks,
>>> David
>>> -----
>>>
>>>> --alex