On Wed, Jul 06, 2016 at 08:54:47PM -0400, Theodore Ts'o wrote:

So we could arbitrarily limit eh_depth to say, 32 levels, or some
such.  That will prevent the malicious corruption, while also making
it very difficult for the malicious fallocate/punch hole workload
scenario to be triggered.

I've decided to apply your patch with the limit raised to 32.  That
should be enough to prevent the malicious corruption cases.

       	  	    	    		  - Ted