From 4d608baac5f4e72b033a122b2d6d9499532c3afc Mon Sep 17 00:00:00 2001 From: Alexander Potapenko Date: Mon, 23 Jan 2017 15:06:43 +0100 Subject: [PATCH] block: Initialize cfqq->ioprio_class in cfq_get_queue() 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 [] dump_stack+0x157/0x1d0 lib/dump_stack.c:51 [] kmsan_report+0x205/0x360 ??:? [] __msan_warning+0x5b/0xb0 ??:? [< inline >] cfq_init_cfqq block/cfq-iosched.c:3754 [] cfq_get_queue+0xc80/0x14d0 block/cfq-iosched.c:3857 ... origin: [] save_stack_trace+0x27/0x50 arch/x86/kernel/stacktrace.c:67 [] kmsan_internal_poison_shadow+0xab/0x150 ??:? [] kmsan_poison_slab+0xbb/0x120 ??:? [< inline >] allocate_slab mm/slub.c:1627 [] new_slab+0x3af/0x4b0 mm/slub.c:1641 [< inline >] new_slab_objects mm/slub.c:2407 [] ___slab_alloc+0x323/0x4a0 mm/slub.c:2564 [< inline >] __slab_alloc mm/slub.c:2606 [< inline >] slab_alloc_node mm/slub.c:2669 [] kmem_cache_alloc_node+0x1d2/0x1f0 mm/slub.c:2746 [] 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. Signed-off-by: Alexander Potapenko Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 37aeb20fa454..c472886c727f 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -3864,6 +3864,8 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic, goto out; } + /* cfq_init_cfqq() assumes cfqq->ioprio_class is initialized. */ + cfqq->ioprio_class = IOPRIO_CLASS_NONE; cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync); cfq_init_prio_data(cfqq, cic); cfq_link_cfqq_cfqg(cfqq, cfqg);