dma-debug: Fix check_unmap null pointer dereference
dma-debug: Fix check_unmap null pointer dereference

While it's debatable whether or not a NULL device argument to
the DMA API functions is valid... since it certainly isn't
valid on devices with an IOMMU... dma-debug really shouldn't be
dereferencing null pointers either.

Guard against that in err_printk and the driver_filter
functions. A Fedora rawhide user was seeing this in one of the
dvb drivers resulting in an oops on boot.

[ A patch has been sent for testing to the driver, but I feel
  the dma debugging support should be fixed as well. (There's
  still a pile of legacy garbage in the kernel passing null
  pointers to dma_{alloc,free}_*. :( ]

Signed-off-by: Kyle McMartin <3c25b01657254677d3e1a8fd1f0742c5d489bd39@redhat.com>
Cc: ad86ba2154032c9f55743a190faa2459a9d61d42@infradead.org
Cc: Joerg Roedel <ebd221a096cbc71dd9e1991db28795933c85f380@amd.com>
LKML-Reference: <a51ac7ca03f7ddc4834f65d16144bd7017dc497d@bombadil.infradead.org>
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@elte.hu>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs