RDMA: Fix software RDMA drivers for dma mapping error

The commit f959dcd6 ("dma-direct: Fix potential NULL pointer
dereference") made dma_mask as mandetory field to be setup even for
dma_virt_ops based dma devices. The commit in the fixes tag omitted
setting up the dma_mask on virtual devices triggering the below trace when
they were combined during the merge window.

Fix it by setting empty DMA MASK for software based RDMA devices.

  WARNING: CPU: 1 PID: 8488 at kernel/dma/mapping.c:149 dma_map_page_attrs+0x493/0x700
  CPU: 1 PID: 8488 Comm: syz-executor144 Not tainted 5.9.0-syzkaller #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:dma_map_page_attrs+0x493/0x700 kernel/dma/mapping.c:149
  Trace:
   dma_map_single_attrs include/linux/dma-mapping.h:279 [inline]
   ib_dma_map_single include/rdma/ib_verbs.h:3967 [inline]
   ib_mad_post_receive_mads+0x23f/0xd60 drivers/infiniband/core/mad.c:2715
   ib_mad_port_start drivers/infiniband/core/mad.c:2862 [inline]
   ib_mad_port_open drivers/infiniband/core/mad.c:3016 [inline]
   ib_mad_init_device+0x72b/0x1400 drivers/infiniband/core/mad.c:3092
   add_client_context+0x405/0x5e0 drivers/infiniband/core/device.c:680
   enable_device_and_get+0x1d5/0x3c0 drivers/infiniband/core/device.c:1301
   ib_register_device drivers/infiniband/core/device.c:1376 [inline]
   ib_register_device+0x7a7/0xa40 drivers/infiniband/core/device.c:1335
   rxe_register_device+0x46d/0x570 drivers/infiniband/sw/rxe/rxe_verbs.c:1182
   rxe_add+0x12fe/0x16d0 drivers/infiniband/sw/rxe/rxe.c:247
   rxe_net_add+0x8c/0xe0 drivers/infiniband/sw/rxe/rxe_net.c:507
   rxe_newlink drivers/infiniband/sw/rxe/rxe.c:269 [inline]
   rxe_newlink+0xb7/0xe0 drivers/infiniband/sw/rxe/rxe.c:250
   nldev_newlink+0x30e/0x540 drivers/infiniband/core/nldev.c:1555
   rdma_nl_rcv_msg+0x367/0x690 drivers/infiniband/core/netlink.c:195
   rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline]
   rdma_nl_rcv+0x2f2/0x440 drivers/infiniband/core/netlink.c:259
   netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
   netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
   netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
   sock_sendmsg_nosec net/socket.c:651 [inline]
   sock_sendmsg+0xcf/0x120 net/socket.c:671
   ____sys_sendmsg+0x6e8/0x810 net/socket.c:2353
   ___sys_sendmsg+0xf3/0x170 net/socket.c:2407
   __sys_sendmsg+0xe5/0x1b0 net/socket.c:2440
   do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x443699

Link: https://lore.kernel.org/r/20201030093803.278830-1-parav@nvidia.com


Reported-by:  <syzbot+34dc2fea3478e659af01@syzkaller.appspotmail.com>
Fixes: e0477b34 ("RDMA: Explicitly pass in the dma_device to ib_register_device")
Signed-off-by: Parav Pandit <parav@nvidia.com>
Tested-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Tested-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Zhu Yanjun <yanjunz@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>