Re: [PATCH net v2] net/sched: serialize qdisc_rtab_list against concurrent get/put

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@xxxxxxxxxx>:

On Wed, 15 Jul 2026 08:41:14 -0300 you wrote:
> qdisc_get_rtab() and qdisc_put_rtab() mutate the process-global singly
> linked list qdisc_rtab_list and a plain non-atomic 'int refcnt' with no
> lock. This was only safe because every caller historically held the RTNL
> mutex, which serialized all rate-table lookups, inserts and frees.
> 
> That invariant no longer holds. cls_flower sets
> TCF_PROTO_OPS_DOIT_UNLOCKED, so tc_new_tfilter() keeps rtnl_held == false
> for it and sets TCA_ACT_FLAGS_NO_RTNL. That flag propagates through
> tcf_exts_validate_ex() -> tcf_action_init() -> tcf_action_init_1() ->
> tcf_police_init(), which calls qdisc_get_rtab()/qdisc_put_rtab() with the
> RTNL mutex NOT held. Two RTM_NEWTFILTER requests on different CPUs, each
> adding a flower filter with a police action carrying the same rate, then
> race on qdisc_rtab_list and on the non-atomic refcnt, leading to a
> use-after-free / double-free of the kmalloc-2k struct qdisc_rate_table.
> qdisc_rtab_list is a single global (not per-netns), so the corrupted
> object is shared system-wide.
> 
> [...]

Here is the summary with links:
  - [net,v2] net/sched: serialize qdisc_rtab_list against concurrent get/put
    https://git.kernel.org/netdev/net/c/f43ee0c0730d

You are awesome, thank you!
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