In commit ec3ed293e766 ("net_sched: change tcf_del_walker() to take idrinfo->lock")
we move fl_hw_destroy_tmplt() to a workqueue to avoid blocking
with the spinlock held. Unfortunately, this causes a lot of
troubles here:
1. tcf_chain_destroy() could be called right after we queue the work
but before the work runs. This is a use-after-free.
2. The chain refcnt is already 0, we can't even just hold it again.
We can check refcnt==1 but it is ugly.
3. The chain with refcnt 0 is still visible in its block, which means
it could be still found and used!
4. The block has a refcnt too, we can't hold it without introducing a
proper API either.
We can make it working but the end result is ugly. Instead of wasting
time on reviewing it, let's just convert the troubling spinlock to
a mutex, which allows us to use non-atomic allocations too.
Fixes: ec3ed293e766 ("net_sched: change tcf_del_walker() to take idrinfo->lock")
Reported-by: Ido Schimmel <idosch@idosch.org>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Vlad Buslov <vladbu@mellanox.com>
Cc: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Tested-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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