On Tue, Oct 02, 2018 at 12:50:19PM -0700, Cong Wang wrote:
> 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 <ido...@idosch.org>
> Cc: Jamal Hadi Salim <j...@mojatatu.com>
> Cc: Vlad Buslov <vla...@mellanox.com>
> Cc: Jiri Pirko <j...@mellanox.com>
> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
Tested-by: Ido Schimmel <ido...@mellanox.com>
Thanks a lot!
