CVE-2026-68090 in Linux
Сводка
по MITRE • 10.08.2026
In the Linux kernel, the following vulnerability has been resolved:
debugobjects: Plug race against a concurrent OOM disable
syzbot reported a puzzling splat:
WARNING: kernel/time/hrtimer.c:443 at stub_timer+0xa/0x20
stub_timer() is installed as timer callback function in hrtimer_fixup_assert_init(), which is invoked when debug_object_assert_init() can't find a shadow object. In that case debug objects emits a warning about it before invoking the fixup.
Though the provided console log lacks this warning and instead has the following a few seconds before the splat:
ODEBUG: Out of memory. ODEBUG disabled
So the object was looked up in debug_object_assert_init() and the lookup failed due a concurrent out of memory situation which disabled debug objects and freed the shadow objects:
debug_object_assert_init() if (!debug_objects_enabled) return; obj = alloc(); if (!obj) {
// Out of memory debug_objects_enabled = false; free_objects(); obj = lookup_or_alloc();
// The lookup failed because the other side // removed the objects, so this returns // an error code as the object in question // is not statically initialized
if (!IS_ERR_OR_NULL(obj)) return; if (!obj) {
debug_oom(); return; }
print(...) if (!debug_objects_enabled) return;
fixup(...)
The debug object splat is skipped because debug_objects_enabled is false, but the fixup callback is invoked unconditionally, which makes the timer disfunctional.
This is only a problem in debug_object_assert_init() and debug_object_activate() as both have to handle statically initialized objects and therefore must handle the error pointer return case gracefully. All other places only handle the found/not found case and the NULL pointer return is a signal for OOM. Otherwise they get a valid shadow object.
Plug the hole by checking whether debug objects are still enabled before invoking the print and fixup function in those two places.
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