• Alexander Potapenko's avatar
    block: Initialize cfqq->ioprio_class in cfq_get_queue() · 4d608baa
    Alexander Potapenko authored
    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: default avatarAlexander Potapenko <glider@google.com>
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
    4d608baa
cfq-iosched.c 127 KB