bug#4291: 23.1; doc-view-mode temporary directory vulnerable to denial of service

[Glenn Morris]

Stefan Monnier wrote:

> Yes, tho it's a bit different: your case can be avoided by appropriate
> use of quotas on /tmp (yes, I realize this is highly unlikely), and your
> case cannot be obtained without impacting the system as a whole
> (i.e. it's less discrete).

The original scenario doesn't seem likely (or discreet). I suggest
just making docview give an explicit error if its cache dir: a) cannot
be created; or b) exists but cannot be read or written to.