usb-storage: alauda: Fix uninit-value in alauda_check_media()

Syzbot got KMSAN to complain about access to an uninitialized value in
the alauda subdriver of usb-storage:

BUG: KMSAN: uninit-value in alauda_transport+0x462/0x57f0
drivers/usb/storage/alauda.c:1137
CPU: 0 PID: 12279 Comm: usb-storage Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x191/0x1f0 lib/dump_stack.c:113
  kmsan_report+0x13a/0x2b0 mm/kmsan/kmsan_report.c:108
  __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
  alauda_check_media+0x344/0x3310 drivers/usb/storage/alauda.c:460

The problem is that alauda_check_media() doesn't verify that its USB
transfer succeeded before trying to use the received data.  What
should happen if the transfer fails isn't entirely clear, but a
reasonably conservative approach is to pretend that no media is
present.

A similar problem exists in a usb_stor_dbg() call in
alauda_get_media_status().  In this case, when an error occurs the
call is redundant, because usb_stor_ctrl_transfer() already will print
a debugging message.

Finally, unrelated to the uninitialized memory access, is the fact
that alauda_check_media() performs DMA to a buffer on the stack.
Fortunately usb-storage provides a general purpose DMA-able buffer for
uses like this.  We'll use it instead.

Reported-and-tested-by:  <syzbot+e7d46eb426883fb97efd@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/all/0000000000007d25ff059457342d@google.com/T/
Suggested-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Fixes: e80b0fad

 ("[PATCH] USB Storage: add alauda support")
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/693d5d5e-f09b-42d0-8ed9-1f96cd30bcce@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>