xfrm6: fix inet6_dev refcount underflow problem

maillist inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I84HSL

Reference: https://lore.kernel.org/netdev/CADvbK_euiOKytyFd6KYgNoM5SbDcyz92Li=K7P48H35q1AFxYg@mail.gmail.com/T/



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There are race conditions that may lead to inet6_dev refcount underflow
in xfrm6_dst_destroy() and rt6_uncached_list_flush_dev().

One of the refcount underflow bugs is shown below:
	(cpu 1)                	|	(cpu 2)
xfrm6_dst_destroy()             |
  ...                           |
  in6_dev_put()                 |
				|  rt6_uncached_list_flush_dev()
  ...				|    ...
				|    in6_dev_put()
  rt6_uncached_list_del()       |    ...
  ...                           |

xfrm6_dst_destroy() calls rt6_uncached_list_del() after in6_dev_put(),
so rt6_uncached_list_flush_dev() has a chance to call in6_dev_put()
again for the same inet6_dev.

Fix it by moving in6_dev_put() after rt6_uncached_list_del() in
xfrm6_dst_destroy().

Fixes: 510c321b ("xfrm: reuse uncached_list to track xdsts")
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Lu Wei <luwei32@huawei.com>
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>