git: f58af5d9c538 - stable/15 - kern: osd: trash a slot's methods upon deregistration

The branch stable/15 has been updated by kevans:

URL: https://cgit.FreeBSD.org/src/commit/?id=f58af5d9c538130d5bcdfabe1d94b56f32aa6fff

commit f58af5d9c538130d5bcdfabe1d94b56f32aa6fff
Author:     Kyle Evans <[email protected]>
AuthorDate: 2026-06-25 03:08:05 +0000
Commit:     Kyle Evans <[email protected]>
CommitDate: 2026-08-06 23:36:03 +0000

    kern: osd: trash a slot's methods upon deregistration
    
    This both lets us quickly identify a slot that's been deallocated while
    debugging, and forces us to take a fault if something tries to call one
    of the methods anyways somehow with osd_destructors[slot - 1] == NULL.
    
    Reviewed by:    imp, jamie
    
    (cherry picked from commit 4ffa7e126ed0081b804bda6fb71a60acf49dabda)
---
 sys/kern/kern_osd.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/sys/kern/kern_osd.c b/sys/kern/kern_osd.c
index b64735e7f93a..94377b39dbc1 100644
--- a/sys/kern/kern_osd.c
+++ b/sys/kern/kern_osd.c
@@ -180,6 +180,18 @@ osd_deregister(u_int type, u_int slot)
 	osdm[type].osd_destructors[slot - 1] = NULL;
 	OSD_DEBUG("Slot deregistration (type=%u, slot=%u).", type, slot);
 
+#ifdef INVARIANTS
+	/*
+	 * We trash the slot's osd_methods upon deregistration so that we take
+	 * a fault if something calls them, rather than potentially
+	 * inadvertently executing some arbitrary function if another module's
+	 * been mapped over the one that deregistered.
+	 */
+	for (u_int method = 0; method < osdm[type].osd_nmethods; method++) {
+		OSD_METHOD(osdm[type], slot, method) = (void *)0xdeadc0de;
+	}
+#endif
+
 	rm_wunlock(&osdm[type].osd_object_lock);
 	sx_xunlock(&osdm[type].osd_module_lock);
 }