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
[<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.
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 37aeb20..c472886 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);