RDMA/cma: Do not change route.addr.src_addr outside state checks

In the Linux kernel, the following vulnerability has been resolved:

RDMA/cma: Do not change route.addr.src_addr outside state checks

If the state is not idle then resolve_prepare_src() should immediately
fail and no change to global state should happen. However, it
unconditionally overwrites the src_addr trying to build a temporary any
address.

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)

Which 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

This 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 derived from the dst build one explicitly on the stack and
bind to that as any other normal flow would do. rdma_bind_addr() will copy
it over the src_addr once it knows the state is valid.

This is similar to commit bc0bdc5afaa7 ("RDMA/cma: Do not change
route.addr.src_addr.ss_family")