unix_bind_bsd(): move done_path_create() call after dealing with ->bindlock

mainline inclusion
from mainline-v5.14-rc1
commit 56c1731b
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4OM1C
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=56c1731b280dc71febf5df80fcac1923ea973ab8



--------------------------------

Final preparations for doing unlink on failure past the successful
mknod.  We can't hold ->bindlock over ->mknod() or ->unlink(), since
either might do sb_start_write() (e.g. on overlayfs).  However, we
can do it while holding filesystem and VFS locks - doing
	kern_path_create()
	vfs_mknod()
	grab ->bindlock
	if u->addr had been set
		drop ->bindlock
		done_path_create
		return -EINVAL
	else
		assign the address to socket
		drop ->bindlock
		done_path_create
		return 0
would be deadlock-free.  Here we massage unix_bind_bsd() to that
form.  We are still doing equivalent transformations.

Next commit will *not* be an equivalent transformation - it will
add a call of vfs_unlink() before done_path_create() in "alread bound"
case.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

Conflicts:
	net/unix/af_unix.c

Signed-off-by: Baisong Zhong <zhongbaisong@huawei.com>
Reviewed-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>