[jcifs] NullPointerException in SmbFile.resolveDfs()

[Brett Johnson]

Mike,

We are using jCIFS v1.3.17.

I searched for "jcifs tconHostName NullPointerException"
and did not find it was fixed.  Several people had encountered
the problem.  Gabor Herr had a proposed patch that seemed to
work for him and another person, but you did not like it, and
left it as a TODO to fix it right.

Most users complained of encountering the NPE during listFiles.
We encountered it when closing an InputStream.  Our application
work-around was to catch the exception and ignore it, since we 
had consumed the input stream and didn't care.

Coincidentally, the google search also returned this page:
http://blog.gmane.org/gmane.network.samba.java/month=20120301

We have also encountered this deadlock (with a different customer).
Although our app is multi-threaded, we were *not* using the same
SmbFile in different threads.  The deadlock occurred when accessing
two different files.  I fixed it in a manner nearly identical to
that proposed by Xavier Roche, and the customer reports no more
deadlock after a week of testing.

--
Brett M. Johnson


On Nov 14, 2012, at 7:08 AM, Michael B Allen <ioplex at gmail.com> wrote:

> Hi Brett,
> 
> I think this has been fixed long ago (Google for "jcifs tconHostName
> NullPointerException").
> 
> What version of JCIFS are you using?
> 
> Mike
> 
> On Mon, Oct 15, 2012 at 6:09 PM, Brett Johnson
> <brett.michael.johnson at gmail.com> wrote:
>> One of our customers have encountered a NullPointerException
>> thrown from deep within jCIFS while closing an input stream:
>> 
>> From a customer log:
>> Exception in thread "..." java.lang.NullPointerException
>> at jcifs.smb.SmbFile.resolveDfs(SmbFile.java:668)
>> at jcifs.smb.SmbFile.send(SmbFile.java:770)
>> at jcifs.smb.SmbFile.close(SmbFile.java:1018)
>> at jcifs.smb.SmbFile.close(SmbFile.java:1024)
>> at jcifs.smb.SmbFile.close(SmbFile.java:1028)
>> at jcifs.smb.SmbFileInputStream.close(SmbFileInputStream.java:104)
>> at java.io.BufferedInputStream.close(Unknown Source)
>> at com.google.enterprise.connector.filesystem.SmbInputStream.close(SmbInputStream.java:64)
>> at com.google.enterprise.connector.util.BasicChecksumGenerator.getDigest(BasicChecksumGenerator.java:117)
>> at com.google.enterprise.connector.util.BasicChecksumGenerator.getChecksum(BasicChecksumGenerator.java:131)
>> at com.google.enterprise.connector.filesystem.FileInfoCache.getChecksum(FileInfoCache.java:59)
>> at com.google.enterprise.connector.filesystem.FileDocumentSnapshot$GetUpdateSupport.getUpdate(FileDocumentSnapshot.java:384)
>> at com.google.enterprise.connector.filesystem.FileDocumentSnapshot.getUpdate(FileDocumentSnapshot.java:141)
>> at com.google.enterprise.connector.filesystem.FileDocumentSnapshot.getUpdate(FileDocumentSnapshot.java:35)
>> 
>> Looking more closely at SmbFile, the NPE is thrown from this statement:
>>   DfsReferral dr = dfs.resolve(
>>       tree.session.transport.tconHostName,
>>       tree.share,
>>       unc,
>>       auth);
>> 
>> I know dfs itself is not null, since it is statically initialized.
>> So the suspects are tree, tree.session, tree.session.transport.
>> Immediately before this statement is a call to connect0.  Examining
>> that code, tree starts out null but I don't think tree can be null after
>> a successful call to connect().
>> 
>> So that leaves tree.session and tree.session.transport.  Since
>> session is a constructor arg for SmbTree, that probably is not
>> null.  That leaves only SmbSession.transport.  When I read SmbSession,
>> transport is initialized lazily and is always fetched via the
>> SmbSession.transport() method.  I think that is the problem here.
>> I think JCIFS could be patched as follows (note transport() method call):
>> 
>>        DfsReferral dr = dfs.resolve(
>>                    tree.session.transport().tconHostName,
>>                    tree.share,
>>                    unc,
>>                    auth);
>> 
>> However, even after this, tconHostName is very likely to be null in the
>> current failure case, since it is populated by a call to transport.doConnect().
>> If domain is null, dfs.resolve() will throw NPE when it dereferences
>> domain (which it does several times).  At this point, I don't know
>> enough about DFS and JCIFS to know how to fix the bug, so I modified
>> com.google.enterprise.connector.filesystem.SmbInputStream.close() to
>> catch NullPointerException and rethrow as IOException.
>> 
>> --
>> Brett M. Johnson
>> 
>> 
>> 
>> 
> 
> 
> 
> -- 
> Michael B Allen
> Java Active Directory Integration
> http://www.ioplex.com/