Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
In the Linux kernel, the following vulnerability has been resolved:mm/kmemleak: avoid soft lockup in __kmemleak_do_cleanup()A soft lockup warning was observed on a relative small system x86-64system with 16 GB of memory when running a debug kernel with kmemleakenabled. watchdog: BUG: soft lockup - CPU#8 stuck for 33s! [kworker/8:1:134]The test system was running a workload with hot unplug happening inparallel. Then kemleak decided to disable itself due to its inability toallocate more kmemleak objects. The debug kernel has itsCONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE set to 40,000.The soft lockup happened in kmemleak_do_cleanup() when the existingkmemleak objects were being removed and deleted one-by-one in a loop via aworkqueue. In this particular case, there are at least 40,000 objectsthat need to be processed and given the slowness of a debug kernel and thefact that a raw_spinlock has to be acquired and released in__delete_object(), it could take a while to properly handle all theseobjects.As kmemleak has been disabled in this case, the object removal anddeletion process can be further optimized as locking isn't really needed. However, it is probably not worth the effort to optimize for such an edgecase that should rarely happen. So the simple solution is to callcond_resched() at periodic interval in the iteration loop to avoid softlockup.
No PoCs from references.
- https://github.com/w4zu/Debian_security