nfc: pn533: initialize struct pn533_out_arg properly

struct pn533_out_arg used as a temporary context for out_urb is not
initialized properly. Its uninitialized 'phy' field can be dereferenced in
error cases inside pn533_out_complete() callback function. It causes the
following failure:

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.2.0-rc3-next-20230110-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:pn533_out_complete.cold+0x15/0x44 drivers/nfc/pn533/usb.c:441
Call Trace:
 <IRQ>
 __usb_hcd_giveback_urb+0x2b6/0x5c0 drivers/usb/core/hcd.c:1671
 usb_hcd_giveback_urb+0x384/0x430 drivers/usb/core/hcd.c:1754
 dummy_timer+0x1203/0x32d0 drivers/usb/gadget/udc/dummy_hcd.c:1988
 call_timer_fn+0x1da/0x800 kernel/time/timer.c:1700
 expire_timers+0x234/0x330 kernel/time/timer.c:1751
 __run_timers kernel/time/timer.c:2022 [inline]
 __run_timers kernel/time/timer.c:1995 [inline]
 run_timer_softirq+0x326/0x910 kernel/time/timer.c:2035
 __do_softirq+0x1fb/0xaf6 kernel/softirq.c:571
 invoke_softirq kernel/softirq.c:445 [inline]
 __irq_exit_rcu+0x123/0x180 kernel/softirq.c:650
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:662
 sysvec_apic_timer_interrupt+0x97/0xc0 arch/x86/kernel/apic/apic.c:1107

Initialize the field with the pn533_usb_phy currently used.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 9dab880 ("nfc: pn533: Wait for out_urb's completion in pn533_usb_send_frame()")
Reported-by: [email protected]
Signed-off-by: Fedor Pchelkin <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

drivers/nfc/pn533/usb.c

@@ -175,6 +175,7 @@ static int pn533_usb_send_frame(struct pn533 *dev,
  print_hex_dump_debug("PN533 TX: ", DUMP_PREFIX_NONE, 16, 1,
  out->data, out->len, false);
 
+ arg.phy = phy;
  init_completion(&arg.done);
  cntx = phy->out_urb->context;
  phy->out_urb->context = &arg;