On Thu, Dec 05, 2019 at 11:29:28PM +0100, Pavel Machek wrote:
Hi!
From: Greg Kroah-Hartman gregkh@linuxfoundation.org
[ Upstream commit 8ed0579c12b2fe56a1fac2f712f58fc26c1dc49b ]
debugfs can now report an error code if something went wrong instead of just NULL. So if the return value is to be used as a "real" dentry, it needs to be checked if it is an error before dereferencing it.
This is now happening because of ff9fb72bc077 ("debugfs: return error values, not NULL"). syzbot has found a way to trigger multiple debugfs files attempting to be created, which fails, and then the error code gets passed to dentry_path_raw() which obviously does not like it.
4.19-stable does not contain patch ff9fb72bc077, so is this still good idea? It should not break anything, as it still uses IS_ERR_OR_NULL, but...
Yes it should as just testing for NULL was incorrect in the first place.
thanks,
greg k-h