| Message ID | 20241206002417.3295533-4-andrii@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Improve performance and scalability of uretprobes | expand |
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index cca1fe4a3fb1..2345aeb63d3b 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2116,12 +2116,12 @@ static void cleanup_return_instances(struct uprobe_task *utask, bool chained, while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) { ri_next = ri->next; + rcu_assign_pointer(utask->return_instances, ri_next); utask->depth--; free_ret_instance(ri, true /* cleanup_hprobe */); ri = ri_next; } - rcu_assign_pointer(utask->return_instances, ri); } static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs,
Ensure that by the time we call free_ret_instance() to clean up an instance of struct return_instance it isn't reachable from utask->return_instances anymore. free_ret_instance() is called in a few different situations, all but one of which already are fine w.r.t. return_instance visibility: - uprobe_free_utask() guarantees that ri_timer() won't be called (through timer_delete_sync() call), and so there is no need to unlink anything, because entire utask is being freed; - uprobe_handle_trampoline() is already unlinking to-be-freed return_instance with rcu_assign_pointer() before calling free_ret_instance(). Only cleanup_return_instances() violates this property, which so far is not causing problems due to RCU-delayed freeing of return_instance, which we'll change in the next patch. So make sure we unlink return_instance before passing it into free_ret_instance(), as otherwise reuse will be unsafe. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- kernel/events/uprobes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)