CVE-2026-68090debugobjects: Plug race against a concurrent OOM disable

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/2d5e320b7ab9b25229ac4331541964a58b5e1d29
• https://git.kernel.org/stable/c/203a965bf2ab43130778d8214fb0c3c8c2d19cdf
• https://git.kernel.org/stable/c/23da32e88627e63e0864f59f4c63a2dc0ab851a3
• https://git.kernel.org/stable/c/d663fbf28b2eebe665bb9cf828d7d528e5a8707e
• https://git.kernel.org/stable/c/e2e255d07723c330dded8e576ce28a8d23a692ce
• https://git.kernel.org/stable/c/c00164c9e7fa6145886ad666806cb5347895de5c
• https://git.kernel.org/stable/c/1f4f02b336c3be125c8fcf87df73db2e0e028b8b
• https://git.kernel.org/stable/c/b81dde13cc163450dcb402dcc915ef13ba241e01