RDMA/cma: Do not change route.addr.src_addr.ss_family

RDMA/cma: Do not change route.addr.src_addr.ss_family

If the state is not idle then rdma_bind_addr() will immediately fail and
no change to global state should happen.

For instance if the state is already RDMA_CM_LISTEN then this will corrupt
the src_addr and would cause the test in cma_cancel_operation():

		if (cma_any_addr(cma_src_addr(id_priv)) && !id_priv->cma_dev)

To view a mangled src_addr, eg with a IPv6 loopback address but an IPv4
family, failing the test.

This would manifest as this trace from syzkaller:

  BUG: KASAN: use-after-free in __list_add_valid+0x93/0xa0 lib/list_debug.c:26
  Read of size 8 at addr ffff8881546491e0 by task syz-executor.1/32204

  CPU: 1 PID: 32204 Comm: syz-executor.1 Not tainted 5.12.0-rc8-syzkaller #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  Call Trace:
   __dump_stack lib/dump_stack.c:79 [inline]
   dump_stack+0x141/0x1d7 lib/dump_stack.c:120
   print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:232
   __kasan_report mm/kasan/report.c:399 [inline]
   kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
   __list_add_valid+0x93/0xa0 lib/list_debug.c:26
   __list_add include/linux/list.h:67 [inline]
   list_add_tail include/linux/list.h:100 [inline]
   cma_listen_on_all drivers/infiniband/core/cma.c:2557 [inline]
   rdma_listen+0x787/0xe00 drivers/infiniband/core/cma.c:3751
   ucma_listen+0x16a/0x210 drivers/infiniband/core/ucma.c:1102
   ucma_write+0x259/0x350 drivers/infiniband/core/ucma.c:1732
   vfs_write+0x28e/0xa30 fs/read_write.c:603
   ksys_write+0x1ee/0x250 fs/read_write.c:658
   do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
   entry_SYSCALL_64_after_hwframe+0x44/0xae

Which is indicating that an rdma_id_private was destroyed without doing
cma_cancel_listens().

Instead of trying to re-use the src_addr memory to indirectly create an
any address build one explicitly on the stack and bind to that as any
other normal flow would do.

Link: https://lore.kernel.org/r/0-v1-9fbb33f5e201+2a-cma_listen_jgg@nvidia.com
Cc: stable@vger.kernel.org
Fixes: d6e68a36cc9f ("RDMA/cma: Make the locking for automatic state transition more clear")
Reported-by: syzbot+6bb0528b13611047209c@syzkaller.appspotmail.com
Tested-by: Hao Sun <sunhao.th@gmail.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>