git: 1120c36b075c - releng/12.3 - vm_fault: Shoot down shared mappings in vm_fault_copy_entry()

The branch releng/12.3 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=1120c36b075c9c0df22fc3d2e870ba8f85ceed2c

commit 1120c36b075c9c0df22fc3d2e870ba8f85ceed2c
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2022-07-25 20:53:21 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2022-08-09 19:58:12 +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
    
    (cherry picked from commit 5c50e900ad779fccbf0a230bfb6a68a3e93ccf60)
    (cherry picked from commit 9a2a2871c4908cfe7012236912918622e0ed0b32)
---
 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 7829b3691d83..efbe0b23f259 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -1884,6 +1884,13 @@ 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);
 			VM_OBJECT_RUNLOCK(object);
 			dst_m->dirty = dst_m->valid = src_m->valid;