Re: Null-ptr-deref due to "sanitized pathwalk machinery (v4)"

[Al Viro]

On Tue, Mar 24, 2020 at 09:49:48PM -0400, Qian Cai wrote:

> It does not catch anything at all with the patch,

You mean, oops happens, but neither WARN_ON() is triggered?
Lovely...  Just to make sure: could you slap the same couple
of lines just before
                if (unlikely(!d_can_lookup(nd->path.dentry))) {
in link_path_walk(), just to check if I have misread the trace
you've got?

Does that (+ other two inserts) end up with
	1) some of these WARN_ON() triggered when oops happens or
	2) oops is happening, but neither WARN_ON() triggers or
	3) oops not happening / becoming harder to hit?