git: 5c50e900ad77 - main - vm_fault: Shoot down shared mappings in vm_fault_copy_entry()
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Date: Tue, 09 Aug 2022 19:56:32 UTC
The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=5c50e900ad779fccbf0a230bfb6a68a3e93ccf60 commit 5c50e900ad779fccbf0a230bfb6a68a3e93ccf60 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2022-07-25 20:53:21 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2022-08-09 19:44:45 +0000 vm_fault: Shoot down shared mappings in vm_fault_copy_entry() As in vm_fault_cow(), it's possible, albeit rare, for multiple vm_maps to share a shadow object. When copying a page from a backing object into the shadow, all mappings of the source page must therefore be removed. Otherwise, future operations on the object tree may detect that the source page is fully shadowed and thus can be freed. Approved by: so Security: FreeBSD-SA-22:11.vm Reviewed by: alc, kib Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D35635 --- sys/vm/vm_fault.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c index 0433b6dd3d7e..8f30c5b93828 100644 --- a/sys/vm/vm_fault.c +++ b/sys/vm/vm_fault.c @@ -2107,6 +2107,13 @@ again: VM_OBJECT_WLOCK(dst_object); goto again; } + + /* + * See the comment in vm_fault_cow(). + */ + if (src_object == dst_object && + (object->flags & OBJ_ONEMAPPING) == 0) + pmap_remove_all(src_m); pmap_copy_page(src_m, dst_m); /*