CVE-2024-26643: Improper Locking

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_tables: mark set as dead when unbinding anonymous set with timeout

While the rhashtable set gc runs asynchronously, a race allows it to collect elements from anonymous sets with timeouts while it is being released from the commit path.

Mingi Cho originally reported this issue in a different path in 6.1.x with a pipapo set with low timeouts which is not possible upstream since 7395dfacfff6 ("netfilter: nf_tables: use timestamp to check for set element timeout").

Fix this by setting on the dead flag for anonymous sets to skip async gc in this case.

According to 08e4c8c5919f ("netfilter: nf_tables: mark newset as dead on transaction abort"), Florian plans to accelerate abort path by releasing objects via workqueue, therefore, this sets on the dead flag for abort path too.