[PATCH] uprobes: get RCU trace lock before list iteration

[Breno Leitao <leitao@debian.org>]

Acquire RCU trace lock in filter_chain() to protect
list_for_each_entry_rcu() iteration, protecting the list iteration in a
RCU read section.

Prior to this fix, list_for_each_entry_srcu() was called without holding
the required lock, triggering warnings when RCU_PROVING is enabled:

	kernel/events/uprobes.c:937 RCU-list traversed without holding the required lock!!

Signed-off-by: Breno Leitao <leitao@debian.org>
Fixes: cc01bd044e6a ("uprobes: travers uprobe's consumer list locklessly under SRCU protection")
---
 kernel/events/uprobes.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index fa04b14a7d72353adc440742016b813da6c812d2..afdaa45a43ac3948f7983175eda808c989e8738a 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1103,11 +1103,13 @@ static bool filter_chain(struct uprobe *uprobe, struct mm_struct *mm)
 	bool ret = false;
 
 	down_read(&uprobe->consumer_rwsem);
+	rcu_read_lock_trace();
 	list_for_each_entry_rcu(uc, &uprobe->consumers, cons_node, rcu_read_lock_trace_held()) {
 		ret = consumer_filter(uc, mm);
 		if (ret)
 			break;
 	}
+	rcu_read_unlock_trace();
 	up_read(&uprobe->consumer_rwsem);
 
 	return ret;

---
base-commit: 5b913f5d7d7fe0f567dea8605f21da6eaa1735fb
change-id: 20241107-rcu_probe-bef660d84990

Best regards,
-- 
Breno Leitao <leitao@debian.org>