On Mon, Apr 09, 2018 at 07:03:46PM +0900, Prashant Bhole wrote: > A use-after-free bug was caught by KASAN while running usdt related > code. (BCC project. bcc/tests/python/test_usdt2.py) > <snip> > > Allocated by task 870: > kasan_kmalloc+0xa0/0xd0 > kmem_cache_alloc_node+0x11a/0x430 > copy_process.part.19+0x11a0/0x41c0 > _do_fork+0x1be/0xa20 > do_syscall_64+0x198/0x490 > entry_SYSCALL_64_after_hwframe+0x3d/0xa2 > > Freed by task 0: > __kasan_slab_free+0x12e/0x180 > kmem_cache_free+0x102/0x4d0 > free_task+0xfe/0x160 > __put_task_struct+0x189/0x290 > delayed_put_task_struct+0x119/0x250 > rcu_process_callbacks+0xa6c/0x1b60 > __do_softirq+0x238/0x7ae > > The buggy address belongs to the object at ffff880384f9b480 > which belongs to the cache task_struct of size 12928 > > It occurs because task_struct is freed before perf_event which refers > to the task and task flags are checked while teardown of the event. > perf_event_alloc() assigns task_struct to hw.target of perf_event, > but there is no reference counting for it. > > As a fix we get_task_struct() in perf_event_alloc() at above mentioned > assignment and put_task_struct() in _free_event(). > > Signed-off-by: Prashant Bhole <bhole_prashant...@lab.ntt.co.jp>
Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org> Ingo, can you make this happen, probably with a Cc-stable as well.
