On 25 Aug 2018, at 0:26, Matthew Macy wrote:
On Fri, Aug 24, 2018 at 15:25 Shawn Webb <shawn.w...@hardenedbsd.org> wrote:

Hey All,

Somewhere in the last month or so, a use after free was introduced. I
don't have the time right now to bisect the commits and figure out
which commit introduced the breakage. Attached is the core.txt (which
seems nonsensical because the dump is reporting on a different
thread). If the core.txt gets scrubbed, I've posted it here:
https://gist.github.com/796ea88cec19a1fd2a85f4913482286a


Do you have any guidance on how to reproduce? The hardenedbsd rev isn’t
useful - the svn commit that it’s based against is what is needed.

For what it’s worth, it’s not a hardenedbsd thing. I’ve been chasing the same one (same offset, same allocation size, same most recent user). Something gets set to zero/NULL. 8 bytes on amd64, so presumably a pointer.

I currently only trigger it on a development branch, but I’ll see if I can clean that up into something I can share tomorrow.

In my test scenario it happens after shutdown of a vnet jail with a few interfaces in it (including a pfsync interface which will disappear with the jail), and new jails are started. It’s pretty reliable.

At a guess something’s wrong with the delayed cleanup of ifnets and vnet shutdown.

Regards,
Kristof
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