netfilter: nft_compat: destroy function must not have side effects

The nft_compat destroy function deletes the nft_xt object from a list.
This isn't allowed anymore. Destroy functions are called asynchronously,
i.e. next batch can find the object that has a pending ->destroy()

cpu0                       cpu1
   ->destroy               for_each_entry()
	                     if (x == ...
			        return x->ops;
                           expr->ops->... // ops was free'd

To resolve this, the list_del needs to occur before the transaction
mutex gets released.  nf_tables has a 'deactivate' hook for this
purpose, so use that to unlink the object from the list.

Fixes: 0935d5588400 ("netfilter: nf_tables: asynchronous release")
Reported-by: Taehee Yoo <>
Signed-off-by: Florian Westphal <>
Signed-off-by: Pablo Neira Ayuso <>
1 file changed