kern/52332: ydc driver: sleep-under-spin-mutex bugs in yds_allocmem

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>Number:         52332
>Category:       kern
>Synopsis:       ydc driver: sleep-under-spin-mutex bugs in yds_allocmem
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 25 08:45:00 +0000 2017
>Originator:     Jia-Ju Bai
>Release:        NetBSD-7.1
>Organization:
Tsinghua University
>Environment:
i386
>Description:
The driver may sleep under spin mutex, and the function call path in file "sys/dev/pci/yds.c" in NetBSD-7.1 release is:
yds_resume [acquire the spin mutex]
  yds_init
    yds_allocate_slots
      yds_allocmem
        bus_dmamem_alloc(BUS_DMA_WAITOK) --> may sleep
        bus_dmamem_map(BUS_DMA_WAITOK) --> may sleep
        bus_dmamem_create(BUS_DMA_WAITOK) --> may sleep
        bus_dmamem_load(BUS_DMA_WAITOK) --> may sleep

These bugs are found by a static analysis tool written by myself, and they are checked by my review of the NetBSD code.
>How-To-Repeat:

>Fix:
The possible fix of this bug is to replace "BUS_DMA_WAITOK" with "BUS_DMA_NOWAIT".