Re: autoloading compat43 on tty ioctls

[nia <nia%NetBSD.org@localhost>]

On Sat, Oct 10, 2020 at 01:33:42PM +0000, nia wrote:
> syzkaller found a bug in tty_43.c which i noticed could lock up my
> system after i wrote a reproducer for it.
> 
> i was curious why 43bsd compat is enabled by default on amd64 then
> noticed it gets loaded by tty if it detects an unrecognized ioctl
> 
> https://github.com/NetBSD/src/blob/trunk/sys/kern/tty.c#L1420
> 
> this seems to be a strange choice, especially on archs that never ran
> 43bsd binaries. were applications relying on these ioctls more recently?
> 
> i'm not familiar with the history of this code, but maybe someone here is

it looks like maxv disabled compat43 in amd64 GENERIC in 2017

https://freshbsd.org/commit/netbsd/src/460aa6eb5b4d8484a9a626a429cbbc6be167d8dca7be2361e93ce118eb4d86ab

is its autoloading by tty an oversight?