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osd: Fix racy assertions

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osd_register(9) may reallocate and expand the destructor array for a
given object type if no space is available for a new key.  This happens
with the object lock held.  Thus, when verifying that a given slot in
the array is occupied, we need to hold the object lock to avoid racing
with a reallocation.

Reported by:	syzbot+69ce54c7d7d813315dd3@syzkaller.appspotmail.com
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Mark Johnston 2021-09-09 09:50:27 -04:00
parent b645ee1815
commit 187afc5879
1 changed files with 6 additions and 3 deletions
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9
sys/kern/kern_osd.c
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@ -156,10 +156,11 @@ osd_deregister(u_int type, u_int slot)
KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
KASSERT(slot > 0, ("Invalid slot."));
KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));
sx_xlock(&osdm[type].osd_module_lock);
rm_wlock(&osdm[type].osd_object_lock);
KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));
/*
* Free all OSD for the given slot.
*/
@ -222,9 +223,10 @@ osd_set_reserved(u_int type, struct osd *osd, u_int slot, void **rsv,
KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
KASSERT(slot > 0, ("Invalid slot."));
KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));
rm_rlock(&osdm[type].osd_object_lock, &tracker);
KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));
if (slot > osd->osd_nslots) {
void **newptr;
@ -300,9 +302,10 @@ osd_get(u_int type, struct osd *osd, u_int slot)
KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
KASSERT(slot > 0, ("Invalid slot."));
KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));
rm_rlock(&osdm[type].osd_object_lock, &tracker);
KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));
if (slot > osd->osd_nslots) {
value = NULL;
OSD_DEBUG("Slot doesn't exist (type=%u, slot=%u).", type, slot);