Author: markj Date: Mon Apr 10 21:01:42 2017 New Revision: 316689 URL: https://svnweb.freebsd.org/changeset/base/316689
Log: Busy the map in vm_map_protect(). We are otherwise susceptible to a race with a concurrent vm_map_wire(), which may drop the map lock to fault pages into the object chain. In particular, vm_map_protect() will only copy newly writable wired pages into the top-level object when MAP_ENTRY_USER_WIRED is set, but vm_map_wire() only sets this flag after its fault loop. We may thus end up with a writable wired entry whose top-level object does not contain the entire range of pages. Reported and tested by: pho Reviewed by: kib MFC after: 1 week Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D10349 Modified: head/sys/vm/vm_map.c Modified: head/sys/vm/vm_map.c ============================================================================== --- head/sys/vm/vm_map.c Mon Apr 10 21:00:47 2017 (r316688) +++ head/sys/vm/vm_map.c Mon Apr 10 21:01:42 2017 (r316689) @@ -1965,6 +1965,14 @@ vm_map_protect(vm_map_t map, vm_offset_t vm_map_lock(map); + /* + * Ensure that we are not concurrently wiring pages. vm_map_wire() may + * need to fault pages into the map and will drop the map lock while + * doing so, and the VM object may end up in an inconsistent state if we + * update the protection on the map entry in between faults. + */ + vm_map_wait_busy(map); + VM_MAP_RANGE_CHECK(map, start, end); if (vm_map_lookup_entry(map, start, &entry)) { _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
