Thanks for all your input, as Nikolay asked if this happens in a normal build, I tried [this test](https://testbot.winehq.org/JobDetails.pl?Key=151060&f101=wow64.report#k1...) on the testbot. It creates a buffer on a page boundary and switches the latter page to PAGE_NOACCESS.
If I interpret the output right it means overrunning in `wine_dbgstr_w` would be save as it then returns just `(invalid)`. This seems to originate from a check with `IsBadStringPtrA`.
Unfortunately this makes it harder to show if a succeeding `ok` gets the `wine_dbgstr_w` executed before the condition is evaluated. Therefore I added the lines with `strlen`, and that one seems to already crash on the succeeding `ok`.
However, as this creates no problem in regular builds I guess another option would be to simply ignore the reading overrun `wine_dbgstr_an`/`wine_dbgstr_wn` by disabling ASan just for these functions.
Thanks again for your help, I will do some tests and report back.