lib/nfs/Connection: fix crash while canceling a failing Open()

The method NfsConnection::CancellableCallback::Callback() will always
invoke NfsConnection::Close() on the file handle, even if the void
pointer is not a nfsfh.  This can happen if the Open() was not
successful, e.g. when the file does not exist.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/lib/nfs/Connection.cxx b/src/lib/nfs/Connection.cxx
index 410711275..c57cb9b79 100644
--- a/src/lib/nfs/Connection.cxx
+++ b/src/lib/nfs/Connection.cxx
@@ -156,8 +156,10 @@ NfsConnection::CancellableCallback::Callback(int err, void *data)
 			   allocated file handle immediately */
 			assert(close_fh == nullptr);
 
-			struct nfsfh *fh = (struct nfsfh *)data;
-			connection.Close(fh);
+			if (err >= 0) {
+				struct nfsfh *fh = (struct nfsfh *)data;
+				connection.Close(fh);
+			}
 		} else if (close_fh != nullptr)
 			connection.DeferClose(close_fh);