svn commit: r304153 - head/sys/dev/syscons

[Shawn Webb]

On Mon, Aug 15, 2016 at 12:56:45PM +0000, Bruce Evans wrote:
> Author: bde
> Date: Mon Aug 15 12:56:45 2016
> New Revision: 304153
> URL: https://svnweb.freebsd.org/changeset/base/304153
> 
> Log:
>   Quick fix for locking fixes in r172250.  The lock added there was per-
>   virtual-device, but needs to be per-physical-device so that it protects
>   shared data.  Usually, scp->sc->write_in_progress got corrupted first
>   and further corruption was limited when this variable was left at nonzero
>   with no write in progress.
>   
>   Attempt to fix missing lock destruction in r162285.  Put it with the
>   lock destruction for r172250 after moving the latter.  Both might be
>   unreachable.
>   
>   To demonstrate the bug, find a buggy syscall or sysctl that calls
>   printf(9) and run this often.  Run hd /dev/zero >/dev/ttyvN for any
>   N != 0.  The console spam goes to ttyv0 and the non-console spam goes
>   to ttyvN, so the lock provided no protection (but it helped for
>   N == 0).
> 

Hey Bruce,

Should this be MFC'd after some point?

Thanks,

-- 
Shawn Webb
Cofounder and Security Engineer
HardenedBSD

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