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drop_monitor: synchronize tracepoint unregistration on error path

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If register_trace_napi_poll() fails in net_dm_trace_on_set(),
unregister_trace_kfree_skb() is called to roll back the kfree_skb
tracepoint registration.

However, tracepoint_synchronize_unregister() is omitted before calling
cancel_work_sync() and module_put(). An in-flight probe executing
concurrently on another CPU could call schedule_work() after
cancel_work_sync() has already returned, leaving a pending work item
scheduled after the module reference is dropped. If the module is then
unloaded, executing the work item triggers a kernel panic.

Add tracepoint_synchronize_unregister() after unregister_trace_kfree_skb()
in the error path, matching net_dm_trace_off_set() and
net_dm_hw_probe_unregister().

Fixes: 7c747838a5 ("drop_monitor: Split tracing enable / disable to different functions")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
Link: https://patch.msgid.link/20260910204612.3762015-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-09-10 20:46:09 +00:00 committed by Jakub Kicinski
parent 455ebeadf7
commit 6a038ef2b5
1 changed files with 1 additions and 0 deletions
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1
net/core/drop_monitor.c
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@ -1173,6 +1173,7 @@ static int net_dm_trace_on_set(struct netlink_ext_ack *extack)
err_unregister_trace:
unregister_trace_kfree_skb(ops->kfree_skb_probe, NULL);
tracepoint_synchronize_unregister();
err_module_put:
for_each_possible_cpu(cpu) {
struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);