[PATCH V2] xfs: fix NULL pointer dereference in xfs_filestream_lookup_ag()

[Eric Sandeen <sandeen@xxxxxxxxxxx>]

If xfs_filestream_get_parent() fails, we have a null pip,
goto out, and attempt to IRELE(NULL).  This causes a null
pointer dereference and BUG().

Fix this by directly returning NULLAGNUMBER in this case.

Reported-by: Adrien Nader <adrien@xxxxxxxx>
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---

V2: skip the goto, because Dave doesn't like it.  ;)

diff --git a/fs/xfs/xfs_filestream.c b/fs/xfs/xfs_filestream.c
index a2e86e8..8f9f854 100644
--- a/fs/xfs/xfs_filestream.c
+++ b/fs/xfs/xfs_filestream.c
@@ -322,7 +322,7 @@ xfs_filestream_lookup_ag(
 
        pip = xfs_filestream_get_parent(ip);
        if (!pip)
-               goto out;
+               return NULLAGNUMBER;
 
        mru = xfs_mru_cache_lookup(mp->m_filestream, pip->i_ino);
        if (mru) {