Re: mmap breakage?

On Mon, Apr 05, 2004 at 12:11:47AM -0400, Alexander Kabaev wrote:
> On Sun, Apr 04, 2004 at 03:12:51PM -0500, Alan Cox wrote:
> > Alfred,
> > 
> > Please try the attached patch.  This problems appears to be a
> > consequence of vm/vm_mmap.c revision 1.180, where as part of a much
> > needed code reorganization for locking the check for the /dev/zero
> > special case got placed after the permissions check for the general
> > case.  This patch simply delays the permissions check for devices
> > until you have the necessary lock to also check for /dev/zero.
> > 
> > Since kan_at_ authored the reorganization, I'm cc:'ing him on this
> > message for purposes of obtaining a review.  (At least one comment
> > should be updated to reflect my code changes.)
> > 
> > Regards,
> > Alan
> > 
> > 
> Alan, Alfred,
> 
> I had the following patch which is currently pending a review by
> Peter Wemm. I meant to commit it on Friday, but ran out of time:
> 
> 
>  http://perforce.freebsd.org/chv.cgi?CH=50213
> 

I believe that there is a problem with this patch.  Specifically, if
maxprot is set to VM_PROT_ALL for devices in mmap(), then the security
check in vm_mmap_vnode() has no effect.  Please take a look at the
entirety of the changes that I propose to mmap().

Regards,
Alan