[PATCH] uprobes: clear extra_consumers before pooling return instances

[Keenan Dong]

ri_pool_push() returns a return_instance to the per-task pool for
later reuse. The pool reset clears cons_cnt, but it leaves
extra_consumers behind.

A reused return_instance can later grow a fresh extra_consumers
array and then reach the cleanup path with a stale pointer from its
previous lifetime, leading to a double free of the recycled object.

Free and clear extra_consumers before putting the instance back into
the pool so every reused entry starts from a clean state.

Fixes: 8622e45b5da1 ("uprobes: Reuse return_instances between multiple 
uretprobes within task")
Reported-by: Keenan Dong <keenanat2...@gmail.com>
Signed-off-by: Keenan Dong <keenanat2...@gmail.com>
---
 kernel/events/uprobes.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 923b24b321cc..24b9884a2667 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1945,6 +1945,8 @@ unsigned long uprobe_get_trap_addr(struct pt_regs *regs)
 
 static void ri_pool_push(struct uprobe_task *utask, struct return_instance *ri)
 {
+       kfree(ri->extra_consumers);
+       ri->extra_consumers = NULL;
        ri->cons_cnt = 0;
        ri->next = utask->ri_pool;
        utask->ri_pool = ri;
-- 
2.43.0