On Mon, Jan 23, 2017 at 4:30 PM, Jens Axboe <axboe@xxxxxx> 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). > -- > Jens Axboe > -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
