On Thu, Jun 29, 2017 at 09:23:33AM -0400, Shawn Webb wrote: > On Wed, Jun 28, 2017 at 06:32:38PM -0400, Shawn Webb wrote: > > On Wed, Jun 28, 2017 at 04:02:37AM +0000, Konstantin Belousov wrote: > > > Author: kib > > > Date: Wed Jun 28 04:02:36 2017 > > > New Revision: 320430 > > > URL: https://svnweb.freebsd.org/changeset/base/320430 > > > > > > Log: > > > Treat the addr argument for mmap(2) request without MAP_FIXED flag as > > > a hint. > > > > > > Right now, for non-fixed mmap(2) calls, addr is de-facto interpreted > > > as the absolute minimal address of the range where the mapping is > > > created. The VA allocator only allocates in the range [addr, > > > VM_MAXUSER_ADDRESS]. This is too restrictive, the mmap(2) call might > > > unduly fail if there is no free addresses above addr but a lot of > > > usable space below it. > > > > > > Lift this implementation limitation by allocating VA in two passes. > > > First, try to allocate above addr, as before. If that fails, do the > > > second pass with less restrictive constraints for the start of > > > allocation by specifying minimal allocation address at the max bss > > > end, if this limit is less than addr. > > > > > > One important case where this change makes a difference is the > > > allocation of the stacks for new threads in libthr. Under some > > > configuration conditions, libthr tries to hint kernel to reuse the > > > main thread stack grow area for the new stacks. This cannot work by > > > design now after grow area is converted to stack, and there is no > > > unallocated VA above the main stack. Interpreting requested stack > > > base address as the hint provides compatibility with old libthr and > > > with (mis-)configured current libthr. > > > > > > Reviewed by: alc > > > Tested by: dim (previous version) > > > Sponsored by: The FreeBSD Foundation > > > MFC after: 1 week > > > > > > Modified: > > > head/sys/vm/vm_map.c > > > head/sys/vm/vm_map.h > > > head/sys/vm/vm_mmap.c > > > > Hey Kostik, > > > > This commit breaks both xorg and shutting down/rebooting. Reverting this > > commit makes my laptop happy again. > > Thnking out loud: would these issues arise due to HardenedBSD using > SafeStack, which relies on libthr's stack code?
Here's a somewhat crude and possibly improper fix that makes my laptop happy: http://ix.io/y6z I'm not sure, though, that really fixes the problem or just dances around it. Thanks, -- Shawn Webb Cofounder and Security Engineer HardenedBSD GPG Key ID: 0x6A84658F52456EEE GPG Key Fingerprint: 2ABA B6BD EF6A F486 BE89 3D9E 6A84 658F 5245 6EEE
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