On 01/23/2017 08:49 AM, Alexander Potapenko wrote: > On Mon, Jan 23, 2017 at 4:30 PM, Jens Axboe <ax...@fb.com> wrote: >> On 01/23/2017 07:06 AM, Alexander Potapenko wrote: >>> KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of >>> uninitialized memory in cfq_init_cfqq(): >>> >>> ================================================================== >>> BUG: KMSAN: use of unitialized memory >>> ... >>> Call Trace: >>> [< inline >] __dump_stack lib/dump_stack.c:15 >>> [<ffffffff8202ac97>] dump_stack+0x157/0x1d0 lib/dump_stack.c:51 >>> [<ffffffff813e9b65>] kmsan_report+0x205/0x360 ??:? >>> [<ffffffff813eabbb>] __msan_warning+0x5b/0xb0 ??:? >>> [< inline >] cfq_init_cfqq block/cfq-iosched.c:3754 >>> [<ffffffff8201e110>] cfq_get_queue+0xc80/0x14d0 block/cfq-iosched.c:3857 >>> ... >>> origin: >>> [<ffffffff8103ab37>] save_stack_trace+0x27/0x50 >>> arch/x86/kernel/stacktrace.c:67 >>> [<ffffffff813e836b>] kmsan_internal_poison_shadow+0xab/0x150 ??:? >>> [<ffffffff813e88ab>] kmsan_poison_slab+0xbb/0x120 ??:? >>> [< inline >] allocate_slab mm/slub.c:1627 >>> [<ffffffff813e533f>] new_slab+0x3af/0x4b0 mm/slub.c:1641 >>> [< inline >] new_slab_objects mm/slub.c:2407 >>> [<ffffffff813e0ef3>] ___slab_alloc+0x323/0x4a0 mm/slub.c:2564 >>> [< inline >] __slab_alloc mm/slub.c:2606 >>> [< inline >] slab_alloc_node mm/slub.c:2669 >>> [<ffffffff813dfb42>] kmem_cache_alloc_node+0x1d2/0x1f0 mm/slub.c:2746 >>> [<ffffffff8201d90d>] cfq_get_queue+0x47d/0x14d0 block/cfq-iosched.c:3850 >>> ... >>> ================================================================== >>> (the line numbers are relative to 4.8-rc6, but the bug persists >>> upstream) >>> >>> The uninitialized struct cfq_queue is created by kmem_cache_alloc_node() >>> and then passed to cfq_init_cfqq(), which accesses cfqq->ioprio_class >>> before it's initialized. >> >> Patch looks fine to me, thanks. Is this a new warning? We don't seem >> to have changed this path in a while, yet I wonder why this is only >> surfacing now. > > This is because KMSAN is a new tool, it's not in the trunk yet. Nobody > could see this warning before. > I don't know if kmemcheck detects this bug (and if anyone is actively > using it for testing either).
Ah gotcha, I read that as KASAN. Then it makes more sense. Thanks for clarifying. -- Jens Axboe
